found a gameboy for $20 worth it

The Game Boy Original Handheld Console you found for $20 is a great deal. Based on current eBay asking prices, it's valued around $72 after fees, and you'd expect to net about $57.16 after selling it, resulting in a profit of $37.16 — an 186% return on your investment. This is a strong "BUY" decision. You can check the live eBay listings to compare and confirm the asking prices for similar items.