Sorry for vagueness.. Meaning, with ease of manufacturing and technology, are there any turn-of-the-century products that cost people at the time $5, but thanks to today's industry kept the $5 price tag for us?
Hmm ... good question. Let me tell you where I think the answer lies: food.
If you adjust for inflation, the prices of many basic foods is less today than it was in 1900. Take flour for example. Page 213 (document page 31) of this U.S. Census document has the prices of many basic foodstuffs between 1890 and 1970. Let's look at flour, which has a listed price of 12.5 cents per 6-pound bag in 1900.
Plop that figure into the Westegg inflation calculator, and you get $3.45. Doing a quick search with Google Shopping, I find a 5-pound bag of Gold Medal Unbleached Flour for $1.98. Six pounds would be $2.40, the equivalent of 9 cents in 1900.
Thus, even though inflation has driven up the cost of flour many times, it is more than 25% percent cheaper today than it was in 1900.