Teachers Pay Teachers has some fantastic content on their site and I don't begrudge teachers for buying them. However I do want to say that teachers pay teachers rips off their content providers heavily. To share as an example, I created a set of resources for my AP class. About 6-10 pages of content each, I decided to help my fellow teacher by selling them for $1.50 a set or $3-4 for a Unit packet. I didn't want to charge fellow teachers a crud ton of money. In the last year, I had around $50 gross sales. My Net return was $22. They took over half of the money I earned for people providing my services. They took out 21.95 for their "service" to me. They then took out a transaction fee of 30 cents for every transaction under $3.00 (So almost everything I created). Then they charged me 42 cents in service fees to send my money to paypal.
When you pay for a 150.00 package, note that the author might be getting $60 in that trade. So buy cautiously.