My MIL is a teacher, and she spends her own money every year on school supplies for her classroom. My FIL usually goes to Sam's Club and just buys everything, and it's really expensive even at club prices. In general, men don't look at prices, they just throw everything in the cart and that's that.
I'm sure he has spent hundreds every year.
I started buying things for her when it goes on sale, we get the Sunday paper and I look through it all for Back to School sales, usually Walgreens has the best doorbuster deals. And Office Depot and Staples also sometimes have good sales.
She buys 5 different color 2 pocket folders for all the kids in her class, plus tons of paper, pencils, mechanical pencils, markers, highlighters, sharpies, composition notebooks, glue, rulers, etc, etc.
I had bought so many supplies one year, I spread it out on our kitchen counter and took a photo, I paid about $30 for nearly $200 of supplies.
Folders were on sale for .05/ea. at Walgreens, some highlighters for .09/ea., multipacks of mechanical pencils for .20 a pack of 5, pencils .19 a pack of ten, etc.
It is upsetting that the OP got taken advantage of. They should really tell people what they are buying, it's a hard pill to swallow when you get ripped off. It really stinks. You would think the school would be honest, saying it only costs "a little more" is really dishonest.