There are tons of good deals on Stetsons, Resistols, etc on eBay. There are two kinds of felts, wool and fur . Fur are more expensive, but will hold their shape better after sweating, raining and subsequent drying out.
Two excellent companies are Fort Western and River Junction. River Junction hats are hand shaped ( brim and crown formed by an actual person). To get the right size for your head, you measure your head circumference in inches or cm and compare it to hat chart on the website, you want it snug but not tight or you're going to be miserable.
If you see a hat on a website, check eBay and you might be able to find the same manufacturer for a really good price. I got a really beautiful buffalo fur Stetson from Fort Western on clearance for under $100. The hatter at Fort Western is a CAS/SASS shooter named "Delmonico". He has some really great threads on the CAS City forum on shaping and sizing your cowboy hats.