"So you can throw away the lame i5 and buy a monster 18-core cpu, without replacing an expensive motherboard and 4 sticks of fast ram. That's common in the mainstream market, get a good mobo (Z270) with a cheap CPU (Pentium), then upgrade (i7) in the future. Only now the jump makes more sense, from 4 to up to 36 threads, while yesterday it was from 2 to 8 threads."
This makes no sense. If you can only afford a $250-$350 cpu, you have no business buying a $300-$600 motherboard that will have most of its sockets disabled because you chessed out on the cpu. Then you expect that same person to throw away the $250-$350 cpu? If they couldnt afford the cpu in the first place they cant afford to $300 away. It will have no resale value...
That person would be far better served going out and buying a $80 mobo and a $220 ryzen 6 core. And then throwing that away, or selling it when they can afford the intel system they really wanted(assuming that still makese sense once they can afford it properly). We are talking about someone who needs more cores, or the whole conversation is moot. So they would start off with a lot more computing power and they start off spending a LOT less. In the end either path wastes the same amount of money(except the ryzen chip will have resale value), but you get better performance at first with the ryzen option.
The 4 core chips on a HEDT platform is an extremely poor use of $s. The only person who would consider them is someone who has a lack of $s; the last thing that type of person should do is spend them on the worst performance/$ you can get.