Nevertheless, such high gains wouldn't be needed at all to kick the VPS farms out of the game. I don't have the VPS farm to testify how much profit they have per $ invested at current difficulty, but I'm sure even more moderate (than 25x) GPU efficiency gains will bring VPS farms in red.
It is a close call actually. If you own the VPS farm like I do (Memset.com) then you're only paying for the small slice of the host hardware (~$0.02/day/quad-Xeon) plus the additional power (20 Watts so ~$0.07/day/quad-xeon). I'm currently getting about 1
BTC/day/50 quad-xeon hosts, or ~$2/day/quad-Xeon - it would stop being profitable after a >20-fold productivity reduction roughly. If you're paying the going rate for your VMs (even if you're using a cheap host like
Memset, hint hint
) of, say, $10/month then they will become unprofitable quite soon (>6-fold productivity reduction/difficulty increase).
It also depends on the uptake by GPU miners. If many decide to switch across then yes difficulty will severely curtail the XPM profits, but since it is not technically trivial to implement there is a strong argument for there being slow and/or limited adoption of XPM GPU mining. BTW, where you can you view the total XPM network hashrate/PPS? With that, and ideally historical data, I could do some forecasting on how long XPM will be profitable to mine with VM farms.
As an aside, someone commented about selling XPM. My view as a miner is that I'm not in the business of cryptocurrency speculation so I sell everything at the current price to BTC. I do then have bots trading BTC/USD to get some upside but alt-coins have too low liquidity and too high volatility to be sensible to trade at this time (unless you've really got nothing else to do). For me its all about automation: human time is very expensive!!
Kate.