It’s about as fast as an 8700K in the real world on games (In recent tests it is much more competitive than 1800X was especially on newer titles) and has more cores than an 8700k to dedicate to specific things via core affinity for virtual machines. i.e., you can dedicate 4 cores (or 8 threads, or even 6 threads) to a gaming VM and still have 4 full cores left over for the host.
8700K? You’d only have 2 full cores left for the host. Or only 2 cores for the VM. So whilst per core performance may be slightly better on 8700K (and there’s much less in it than there was with 7700k/8700k vs 1800x), the granularity you have for resource splitting is much worse.
It is well within budget, the motherboards can be obtained cheaper, etc.
Plus you have socket AM4 being supported until 2020 at least.