Finance (or maybe HR if it's an after-hours perk or something) gets incentives/kickbacks? Can anyone that works in this area confirm?
Whoever is earning the rewards can earn quite a bit by choosing a higher priced options since it earns them more.
Preferred supplier relationships are common in corporate America, for example "all employees fly United unless United doesn't go there," or "all employee car rentals are with Avis unless Avis doesn't serve that airport," or "all employee computers are HP unless there is a special exception," etc.
Perhaps you're speaking more generally, and saying that you've never heard of shady decisions made by HR dudes? Well, I have heard of such decisions, and I doubt I'm alone.