I bought 3070s for many reasons.
1) I can get decent mh/s on one rig not have 2 rigs. Used all old stuff I already had with new corsair psu's.
2) Power is highest price in world where I live, currently almost 1/3 my income goes straight to power (more if there is no sun for solar).
3) If something does happen and mining is not worth it 3070 are sell able, 1660super good luck selling tons of them for decent price. At least in my location.
4) Setup cost was pretty much risers, gpus and 2 psu so roi is quicker. 1660supers would mean need way more setup gear.
It still depends on how much you buy your GPU, I bought gtx1660 350$ to 450$ and I bought my 3070 for 1400$ if bear market comes believe me a new 3070 will cost 700$ at the time that's half of the price they are been sold right now