That price is correct for over .25 inches thick....but if your envelope is UNDER .25" , and BENDABLE, the price is 70 Cents. So lay them out thin ladies and no stiff cardboard. Read the postal regulations to know the definition of bendable and take a copy when you go. They will drop your envelope through a .25" slot to confirm thinness.
I'm sorry to report we have 2 post offices near us, and one will type for 15 min trying to charge me the highest price they can , the other post office will charge correctly and talk to me about options.
If you need more information, like postal regulation number/copy or how to lay out 50 charms under .25", let me know. Let's use the system to our favor because there are many more birthdays to go.