Shopgoodwill routinely cites any existing appraisal to set a reserve, even though appraisals are 200% to 300% more than what you can buy the same thing at Costco.
Shopgoodwill flogs very poor diamonds coyly presented for sale without any meaningful description. If you can live with a low-quality diamond, you can get a pair of 3mm, I1 clarity diamond stud earrings on eBay for something in the neighbourhood of $100. Don't get screwed on Shopgoodwill.