50-55 MH/s @ about 150-160W. and they cost under $500 right now.
if you assume the 20 series cards will be the same power efficiency, this is what kind of hashrates they'd have to produce to justify the price over a used 1080ti. (based on EVGA prices for the cheapest 20 series models they have right now)
2080 - 80MH/s
2080ti - 120MH/s
i just dont see that happening.
Yes i expect them 20-30 % only more efficient, but also as ethereum mining is Memory focused , none has tested yet how GDDR6 could work.