We don't know Newegg's margins. Perhaps the board cost them $450 in the first place so paying $100 to repair it so that they could sell it for $500 wouldn't make sense.
You have a broken product. You may have already spent 450$ to get it, but that's sunk cost. You have 3 options:
1. you pay $100 dollars to have a working product (you can sell it for $500).
2. you can engage in fraud and sell this broken product.
3. you write off this loss.
if you discount committing fraud, then the 100$ repair fee definitely makes sense.