Thanks much, Jean!

I loaded up with numerous books of "forever" stamps around 15 years ago and am just about out. This seems shockingly high. Good thing that we use the mail for a very tiny fraction things that we did before. 

https://www.johnstonsarchive.net/other/postage.html

History of United States postage rates

https://en.wikipedia.org/wiki/History_of_United_States_postage_rates