My 1060 3gb versions can't do more than 18,6 Mh/s on Ethash algorithm... Bad RAM.. :/
I am using them on equihash with cca 280 sols/s, which is fine for 210$ card

Are you using dstm's equihash miner? It's titled "zm". I was getting 270 sols with it but get closer to 300 now on my PNY 1060 3gb cards at 65% power. I was really surprised to see the increase. Mine have the better memory though but I don't think it would cause me to get better hash rate on equihash.