The PSA vs SGC difference might make the most sense, but it's hard to believe there is that big a price difference. Here's another example where the 1952 Topps House Yellow Tiger variation went for way more in REA as a PSA 5.5 compared to an SGC 5 in Heritage, and the one in the PSA holder has a print line that goes across his face.
https://bid.robertedwardauctions.com...e?itemid=72212
https://sports.ha.com/itm/baseball/1...umbnail-071515