Hmm, I try to stay away from sketchy sellers.
One time I bought an entire old label CGC 9 / CGC 9.5 Poncho Wearing Eevee collection ($2,000+) from a low-feedback seller on eBay before the authenticity guarantee existed. The listing suggested that the package would ship from Arizona, but it actually shipped from Israel. I was 100% sure that it would arrive with junk, and that I would have to contact eBay for a refund.
Long story short, the package arrived in ~5 days. The seller had declared the package’s worth at $50 for Israeli and U.S. customs. I opened it up, and it was the real deal. I was so relieved.