Regarding tf2 prices

Backpack.tf

https://calculator.tf/

if you want to take the work out of it, and get just a little less per key, scrap.tf is buys keys for metal, all automated, they buy hats, weapons etc etc, but most handy is the autosmetler, turn all your scrap into refined in a single trade instead of doing manually. they also buy commen weps at 1 scrap per 2. same as in game, but dont have to be same class.