Added to the points already made, BP breeding isn't a quick affair. A mammal goes into estrus, has a couple days of being receptive, and she's done. Humans are so good at breeding mammals, you can store sperm for a stud, freeze it, and use it years later. Used that way, a male can sire offspring with a very large number of females with next to no effort. . . . Which has led to the efforts to limit the use of popular sires to reduce inbreeding in some circles.
A female python might allow a male to breed her for months before she ovulates -- if she ovulates at all. If it's a small male, using him on multiple females can be incredibly taxing. So, assuming the male is going out to the female, you're boarding him for at easy six months (three months of QT, then figure another three months minimum of breeding). Doing the reverse, sending the female to the stud . . . BPs can be so touchy about their conditions, I'd suspect a large percentage of females wouldn't got at all.
Breeding loans and agreements are done, sure. But they aren't done on the scale of mammal breeding because the rules are so very different -- they just don't make the same kind of sense.