I have rigs with 6 GTX1060's in that draw less than 600W so, you could easily run this many GPUs with 3 'normal' PSUs.

I'm using 1600W PSUs for most Rigs now - but they're not expensive as I get them from the big Chinese suppliers, or buy chassis which come with them already provided.

If people are going to their local PC suppliers they won't find much over 1000W and will pay high prices, but you can get decent PSUs for mining at decent prices now. Especially for Mobo's like this one where the GPUs are split into groups again.