Looks like a floating point to string conversion error on eBay's end. Some other prices on 10 cent intervals are doing the same (.20/ .30/ .60) but some work (.10/ .40) Each has 0.19 added. Maybe an ampersand getting mixed in? it's ASCII 38, shifted right that's 19. or DC3 is 19. whatever.
For workaround, going to three places with 50.201 works for 50.20, but at 50.601 it doesn't work. You could request 50.19-50.21 and then filter out the incorrect price in the response if that's workable for what you are doing.
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