Last month i get a whole rig with 8x RTX2060 Super for 3000€, so 3000$ for this rig is to much in my opinion.
If the rx570s are 8gb versions then 30+ MH are guaranteed from the cards, that's 62-64MH and as for the p106-100 they only deliver 24MH per card I believe and the p106-90 a little less, honestly to me this isn't worth it, I'd spend the money on 3060ti, you can get 120MH+ from two rtx3060ti cards and the power draw is way lesser, that's just 240watts @ 120MH, way cooler
The P106-100 deliver only 21 - 23mh at the moment, depends on your power setting -> decrease every new DAG epoch.
The P106-90 can´t mine ETH - because it has only 3GB.