They don't actually have to pay for it by using "domain tasting" which gives them the option to grab the domain for up to 5 days. https://en.wikipedia.org/wiki/Domain_name_front_running

I use Dynadot, and they actually pass the "domain tasting" on to the customer: you have a couple of days to cancel your domain registration for a full refund.

As a customer, I highly recommend Dynadot (low prices like NameCheap, but a nicer interface - I tried both registrars when I switched my domains away from DreamHost).

So just wait 5 days to register?

They re-register

Not really, no, because IIRC registers can "return" a domain within a period of time for free or nearly no cost.

Not really. They're a registrar, those domains do not cost them a lot to hold.