You were no way out of line with your pricing on a King Size quilt... I made a T-Shirt quilt for someone and it was queen size. I charged $500 and the women was happy to pay it....
Also doing the binding on a quilt for someone a queen size and and am charging her $40 just to make the binding sew it on by machine and then sew it down by hand and she is happy to pay for it... I'd never take just $200 for a queen size quilt you'd be paying more for material... backing batting and thread...