Help with aquatic turtle costs?

i found my turtle, so it was free. At the pet store, turtles go for about $20. I already had a tank, but if you needed yo buy one, a 50 gallon aquarium would probably cost $100 used. But if your turtle is smaller, a 30 gallon could do, for about $50. Turtle food is relativley inexpensive.. only a few dollars. I just used a brick and a large rock for a basking region. My filter cost only $15, and the decorations only like $10. UV lightbulbs only cost about $5.