By today's standards, and even back then, the British taxes were not unreasonable toward the American colonies. Indeed these taxes were enacted to pay for the French and Indian War, which the colonists did instigate. However, the main issue of the time was not the amount of money these taxes cost (they were fairly affordable), but rather the fact the British Parliament enacted them without the consent of the colonies. The colonies had grown quite used to self-government by this time since Parliament and the British government did not venture to North America that often, and they loved it. Following the war, the British tried to reassert some control by passing taxes, in addition to paying for the war. The colonists were more upset by Parliament's decision to pass these taxes, even though the colonies were not fairly represented in Parliament. Colonists thought of themselves as equals with the rest of Britain, while, in the eyes of the British, Americans were their subordinates since they were colonies under control of the British Empire. So, the main issue being the lack of representation in Parliament led to the obvious rebellion and subsequent American Revolution.

So to answer your question, the taxes were reasonable, but the colonists were upset they were not consulted before the decision was made.

As /u/bleedcubsblue23 has pointed out the main issue that the colonists had with the new taxes being levied by Parliament were either that they considered them to be unfair because the colonists weren't represented, or because of the way in which they were implemented.

The first major resistance to British taxation policy came because of the Stamp Act. The Stamp Act required a stamp to be purchased and applied to nearly every piece of paper, from playing cards to wedding certificates and more. Almost every piece of paper dealing with the maritime trade was to be stamped--which was a particularly hard burden for New England as their economy was based around the sea.

The truly onerous part of this tax was that the stamps had to be paid for in hard currency, which was in incredibly short supply thanks to British monetary policy. The colonial economy largely ran on credit, and if currency was used it was temporary notes printed by the individual colonies for emergency purposes. Those notes could vary in value from colony to colony--a three pound note printed in Massachusetts might be worth more than a five pound note printed in Pennsylvania).

The economy ran on a system of "Pay, money, pay as money, and trusting".

Pay is commodities like grain, beef, pork, etc. with prices set by the General Court.

Money is pieces of eight, rials, Spanish dollars, Massachusetts Bay shillings (which were coins), or any other silver or gold coinage. Interestingly enough wampum was also often used as money--or at least valued as change.

Pay as money is the commodities but 1/3rd cheaper than the price established by the General Court.

Trust is basically credit with terms established between the two parties.

Property was often sold with two prices. One price was the price if purchasing on credit, the other price for cash customers.

This lack of money (especially in property) could lead to massive debt across the colonies. When debt was called in, debtors had to pay in hard currency. This often meant that property was seized for debts paid and sold at a fraction of the value, or if they paid debt with property had to sign over property worth far more than the debt that they owed.

One other problem with the Stamp Act was the wording which stated that the revenue stamps had to placed on all documents in any “court exercising ecclesiastical jurisdiction within the said colonies.”

That bit about the courts and the ecclesiastical jurisdiction was troubling to New Englanders who saw in it an attempt to lay the groundwork for a state sponsored church.

The Townshend Acts were another set of laws passed that on the face of it weren't too onerous, but which were very hard on the colonists. The Townshend Acts had several parts. The first was the Revenue Act, which shifted the taxation from "internal taxes" (which were the stamps), to "external", under the mistaken idea that the colonists had objected to the Stamp Act as unconstitutional because it was an internal tax. Certain items imported from Britain were taxed heavily. Not necessarily a huge deal, except for Britain's earlier trade policies with America which had mandated that the colonies could only buy certain goods from England and only sell certain goods.

Along with the Revenue Act Parliament passed the Indemnity Act, and the Customs Act.

The Indemnity Act was passed to help prop up the East India Tea Company by giving their tea discounts when it was shipped to England. The revenue lost from that would be made up through the taxes imposed on tea imported by American colonists.

The Customs Act gave broad powers to the Admiralty to fight against smuggling. They received widened powers to search vessels and warehouses suspected of smuggling goods. Seamen's personal chests were also searched and contraband seized (previously seamen's personal belongings had been off limits). Captains who were accused of smuggling had their goods and ship seized, and then they had to go to court to prove that they were innocent of smuggling. To defend themselves in court they had to post a bond, and of course any fees required by the court had to be paid in hard currency, which was still in incredibly short supply.

Men who were accused of smuggling weren't given trials by juries either, but were tried in separate Admiralty courts. The Sugar Act of 1764 also established numerous rules and regulations, along with associated fees and fines for breaking those rules. When the Declaration of Independence talks about "swarms of Officers", this is one of the main things it's referring to.

People often point out that the Tea Act of 1773 actually decreased the price of tea. This is true, but it also misses the larger picture. The Tea Act allowed the East India Company to export it's tea directly to America--previously it had been required to sell it's tea at auction in London and merchants would then pass it on. In addition, tea exported to America and the other colonies would either not have to pay export duties, or would have those duties refunded. Finally, consignors in the colonies who sold the tea would be required to pay a deposit--which meant that they stood to potentially lose great amounts of money if the tea didn't get sold or if the price dropped. Also merchants who bought and sold tea from London dealers stood to go bankrupt. Finally, the passage of the Tea Act signaled to colonists that Parliament wasn't listening to them and didn't much care about them.

One other point I want to make. A large portion of the discontent over the taxes came because of England's trade policies with the American colonists. There were numerous laws in place which dictated what goods Americans could produce in America. There were laws which detailed what goods Americans could sell on the open market, and which goods America had to sell only to England. There were also laws which dictated what goods Americans could buy on the open market, vs what goods had to be purchased only from England. What this did was stunt the economic growth of the colonies and lead to situations where Americans sold raw goods at discounted prices to English merchants, and then had to buy finished goods of inferior quality at marked up prices (sometimes substantially marked up). George Washington was one of many people who pointed out that this trade imbalance was a sort of taxation all on it's own.

TL;DR

No, the actual value of the taxes being imposed on American colonists wasn't that great. However the combination of the taxes, the way in which those taxes were collected, the lack of representation in Parliament, and previous Acts which had stunted economic growth made the taxes more onerous than they would have otherwise been.

Fun Fact: The phrase "No taxation without representation was actually coined by an English newspaper editor who was summarizing a speech given by Charles Pratt, First Baron Camden in 1766 as he was protesting the Declaratory Act.