For whatever reason, a lot of people equate 'great' with 'expensive'. Yes, great can mean expensive, but it doesn't have to be that way. A great BP can be built for relatively cheap amounts. The best closers/relievers often come out of nowhere.
Kimbrel's market seems to be dwindling, but I'm guessing he will still get a lucrative deal. Not anything close to the $100 mil though.