For those who have St. Vincent dePaul thrift stores in your area, you may find some good buys there. I pay $1.50 and $1.99 for my flat sheets. I don't know if they have a standard price guide in other states, but I do know that in OHIO they are very reasonable. I use them on the backs of my quilts. I have even gotten some to make curtains. I no longer shop at Goodwill because they have gotten so high.
Please tell us about the Thrift stores in your area and how their prices are. We can all use a good trip to a Thrift store and help a charity at the same time.
June in Cincinnati