Be careful when comparing core counts across providers. Those ultra cheap providers are using servers that can be many generations old. They might also be heavily oversubscribed. 4 vCPU on one of the cheap providers could be slower than 2 vCPU or even 1 vCPU on a newer generation server. You really have to test or look at benchmarks.

If you have a RAM-constrained application where CPU and RAM speed are less of a priority, they can be great deals though.