I've always wondered about this, at Amazon and also at Uber/Lyft/DoorDash etc... They seem to burn through people quite fast. Won't they all just run out of people at some point, or will just increasing pay bring enough people back?
They can only increase pay so much before they have to increase their fees beyond the point people are willing to pay them. As an anecdote, I have completely stopped using DoorDash because they recently increased their fees to a level that I consider to be absurd.
I've noticed our grocery delivery services doing that, too, giving us prices on items that are higher than they are if you go to the store yourself. We'll stop using them soon. It's bullshit. Delivery costs ought to be transparent.
[EDIT] Oh, and places like pizza joints that already had delivery service are starting to get a lot more aggressive about differentiating delivery vs. pick-up pricing. They've long had a deal or two at a time that's carry-out only, but now it's all the decent deals, and even some deals specify that they'll be less-good if you order delivery. Delivery can easily be 40% more expensive than carry-out, as a result, because they also still charge the delivery fees they all started tacking on a decade or so ago (which are also higher, now) and you still, despite already potentially paying $10+ more than you would have for carry-out, have to tip, because most of that money's not making it to the delivery driver.