It depends on what kind of dumbbells you buy. There are rubber-coated, spray-painted, electroplated, foam, bone, plastic-dipped dumbbells, etc. The prices of these dumbbells are different, and they are cheap. Affordable, I personally recommend the ones that are dipped in plastic. For example, if you buy a six kilogram dumbbell, it is not expensive if it is dipped in plastic. I once bought one that was dipped in plastic at CUHK, but there are many dumbbells of various categories there. Let me give you a reference. Take a look at the picture
The dumbbell at the bottom is a plastic-dipped dumbbell