Likely, newegg would refer you to the pc maker who is prepared to handle warranty and defective parts.
They do not test the products. They likely would return it to the manufacturer if they agreed to take the return.
It is not fair to expect a business to take in returned products which they then need to resell as opened box units for a loss.
a 15% restocking fee is reasonable. Many sellers will refuse to take a return altogether.
That said, contact newegg customer support and see if you can negotiate.
I think they would be receptive if you said you ordered the wrong unit and would buy a different unit.