Here are some good places to find used dolls:
Once Upon a Child-OUAC is basically a Goodwill that focuses mostly on children's clothing and toys but sometimes you can find an AG doll or two there. The bad part is that the dolls sell out quickly! If you find a doll buy it as soon as you see it! Oh, and if you have one in your area, you should follow it on social media because most QUACs post when they get AG dolls. The dolls themselves cost 30-80 dollars.
eBay- I have gotten tons of AG stuff on eBay. The thing with eBay is that the sellers are usually AG collectors, so they know how much they can sell the dolls for, although you can get lucky. I found a Pleasant Company Kaya IN BOX NEVER OPENED for $20 the other day! Generally, dolls from eBay that are used and in need of tons of TLC are $10-$35, dolls in gently used condition are $35-$65, dolls in great condition without box are $50-$85, dolls in box you can get on the AG website right now are $80-$125 and retired dolls in mint condition are $125+.
Those are the two ways I get my dolls. If you have any other ways to get AG dolls on the cheap, just comment below!