Around 15 - 20 bucks depends on the breed andor age some cost over 100 bucks :D
If you buy a red eared slider at a pet store the turtle is normally around $20-$30.00. This is only the turtle you would need a tank, filter, basking post, basking light and heater if it stays below 73 in your tank. So all of that can get expensive! I bought a 55 gallon tank kit at Petsmart for $150.00 with everything in it but, basking light, basking ramp and turtle food. Eventually you will have to upgrade your filter it's better to try to get a really good one when you set up. So with all that I would say around $230.00. If your turtle is 3 inches or so you can get a smaller tank like a 30 gallon. Eventually you will at least need a 55 gallon. They are so worth it!!!
YEAH BUT how much do map turtles cost. Because I got one from the backyard and I want to know just in case I sell it