A similar question was asked before with number of answers by /u/Yawarpoma, /u/davratta and others.

#Cost

I'll just add some of my own thoughts. As given by the article linked by /u/Yawarpoma "Columbus's First Voyage: Profit or Loss From a Historical Accountant's Perspective", the cost of Columbus voyage is usually estimated at 2,000,000 maravedis (some estimates go down to 1,140,000 maravedis, some up to 4,000,000, but 2 million is commonly accepted).

You can further read the breakdown of the cost in old work by Thacher "Christopher Columbus: his life, his work, his remains..." around page 474. He does make a possible mistake by estimating the monthly salary of mariner at 500 maravedis, while other evidence point out it was more like 1000. But his work is still valuable. It is worth noting that 2 ships, Nina and Pinta were given free of charge, as part of settling an old debt town of Palos had to the Crown, while Santa Maria had to be charted. Total number of men on the ships was around 90.

Magellan's expedition was different, much bigger and costlier. Luckily we actually have exact data of it's cost. The total of Magellan's preparation was 8,751,125 maravedis, for buying and repairing 5 ships and paying the crew of about between 235 and 270 men. Totals are given in this table (source) and the full itemized list can be seen here.

The costs for both Columbus and Magellan's expeditions aren't final, as the crew was only paid 4 month advance, and the rest of it would be paid after coming back, if they came back that is. We don't have this data. Further more, we shouldn't lose sight that the expeditions themselves were also part commercial, and the ships carried items to trade in the new lands which were to be brought back to Europe and sold, profit of which was to cover part or hopefully total of the costs of expedition. Neither Columbus nor especially Magellan's expedition really succeeded in covering their initial costs, but this information should be kept in mind when analyzing the cost.

#Context

So far we only talked about the cost in maravedis, but this doesn't mean much to us today, does it. We can't really just convert such old money to modern values, as so much of things and prices are different. I can attempt to give values of how much expeditions cost relative to wages, relative to some items, and relative to overall budget.

From an earlier post of mine:

The Magellan list gives prices of different items as well, such as weapons (list link) or foodstuffs (list link).

The monthly salary of a mariner on Magellan voyage was 1,200 maravedis per month, and according to Warriors for a Living: The Experience of the Spanish Infantry in the Italian Wars, 1494–1559 by Idan Sherer, wages of Spanish pikemen was 900 maravedis per month and arquebusier earned 1200 maravedis per month. Here are some wages of professions from the same book.

Also here is a index of wages and prices of various items in 16th century compiled in book Spain's Men of the Sea: Daily Life on the Indies Fleets in the Sixteenth Century by Pablo E. Perez-Mallaina.

If we assume the average salary of a soldier or mariner as 1000 maravedis, we can see that Columbus expedition (at 2 million maravedis) would be enough to equip and pay yearly salaries of about 150-200 soldiers. Magellan's expedition would pay about 700-800 soldiers for a year. That's a lot but not nearly that much.

If we compare the costs by some items, e.g. a live cow that cost 2000 maravadis for Magellan's expedition, we can see that Columbus voyage could pay for 1000 cows, and Magellans for over 4000!

Lastly I tried to find data of budget of Spain of the time, to calculate what would be the percentage the voyages had taken. It wasn't as straight forward affair as I hoped,there are multiple estimates and numbers, some cover whole of Spain, some just Castille, some unspecified. Further complicating things is the fact that in years 1480-1500 there was large reorganization of Spanish finances, with income increasing by several times during period.

For example, here it says the royal revenue of Castille was in 1482 the sum of 150,695,288 maravedis, while in 1504 it was 341,744,597.

Also from "Florins, Faith and Falconetes in the War for Granada, 1482-92" by J Clark (PDF):

According to John Edwards, "the monetary unit of account in late medieval Castile was the maravedí," and the real was worth 34 maravedís. By these figures, Ferdinand and Isabella increased their tax revenue from 30.6 million mrs to 884 million mrs during their reign. See Edwards, Ferdinand and Isabella, 178. For the tax figures, see Jean Hippolyte Mariéjol, The Spain of Ferdinand and Isabella, trans. and ed. Benjamin Keel, (New Brunswick: Rutgers University Press, 1961), 215. See also Jocelyn Hunt, Spain 1474-1598 (London: Taylor and Francis Limited, 2000),

So several amounts float around. I'll just use value of Castille (direct and only sponsor of Columbus) and use it's lowest value of 151 million maravedis revenue in 1482 (and it was probably higher in 1492). Columbus voyage of 2 million maravedis maximum is only 1.3% of the total, low estimated, revenue. I don't have an estimate of expenses, which is admittedly a problem but this might help put things into perspective. And also I don't have info for Magellan's time, but given that at that Charles V ruled Castille, Aragon, Germany, Netherlands and many more, his revenue could only be higher.

#Space program

I know little of space programs, or the US in the 1960 but from some basic info, its obvious those are two very different programs and its hard to draw parallels.

In their very essence space programs like Apollo had very little direct commercial prospect, unlike Columbus and Magellan's expeditions which hoped to open favorable trade opportunities, so any investment was always hoped it would pay itself. Space program not so much (I assume). Space program was a multi-year project, which needed special built machines and vessels, while Magellan and Columbus used normal everyday type of ships. Those ships were even bought (or leased) used and refitted, and not like in NASA case purpose built.

Second, budget of Space programs was out of world. Some info on the internet showed that e.g. at its peak Apollo program employed over 34,000 people directly for NASA and over 375,000 people as contractors. The budget itself, which /u/davratta says was "By 1969, NASA's budget was down to 4.251 billion and just 2.31 % of the Federal spending that year" so over 4 billion USD of the time. 2.31% is double the 1.3% of Columbus, but we should remind ourselves it is only the lowest estimate.

If my google skills are okay, average yearly salary in the 60s was ~$7,000 per year, which means the yearly budget of NASA could pay over 600,000 yearly wages. Contrasted to Columbus and Magellan time where the expedition could pay 200-800 men wages, you see the enormous gap.

As for the cow index, I am unsure how much would the cow go for in the 1960s, but if I take today's price of circa $1500 for a cow, NASA budget could buy 3,000,000 cows, compared to puny Columbus 1000.

Again I am not an expert on the space program, and my numbers for the space program are sometimes approximations, but it gives the rough estimate of just how vastly different these programs are