I recently bought a Pro-SD body to replace an older body that finally gave up and didn't seem worth repairing. Usually I find the KEH price premium to be worth it. Generally anything KEH grades as "bargain" and up is perfectly usable, and EX and EX+ are, well, excellent. You'll be happy with it. If and when they do make a mistake, or you just don't like the item, they'll take a return no questions asked. If you want to avoid the potential stress of getting stuck with a lemon on Ebay and don't mind spending more KEH is the way to go in my opinion, as is Roberts (aka UsedPhotoPro).
In the case of the RB67 however the KEH options just seemed too expensive. There are tons of RB67s out there. The ProSD is a bit harder to find that its predecessors, but not by much. In the end I was patient and found a seemingly never-used SD-Pro (still had the front and rear body caps installed) on a 7-day auction. There were few bids and I got it for less than half what KEH wants for the EX-grade body. I've seen others in good, but not mint, condition go for similar prices on Ebay when auctioned. If you are patient I think you'll be able to find one in nice shape for a decent price. At least a decent for 2023 price... the days of buying RB67s for $50 are probably gone forever.