In the US 1/20/24 was the last day to buy stamps at the old postage rate. The flat rate for postcards was 51 cents and was going up to 53 cents the next day.
They have a concept called forever stamps for regular letters and a similar thing for postcards. If you buy them today at today's price, you can use them at any time in the future regardless of price increases. So if you'll mail letters or postcards, they're a good deal and future investment.
So anyways we ran to the post office at 4pm. The office was closed except for the self service machine. We need about 90 postcard stamps so I figured I'd get 100 to have some extras for the future.
Looking at the machine, I say you got bamboozled. The question at the top of the menu is "What kind[...]?" But yeah, maybe do a sample test run next time around.