Mining is like a high risk investment, and there are so many uncertain things which you can not simply put the number in and calculate it.
So let predict the future:
Situation 1: ETH price going up in the next 3 months, as well as the difficulty, so you still can ROI within 3 months, thanks to ETH price.
Situation 2: ETH price stay in the range of $200-$250 in the next 3 months, but the difficulty still increase, so your calculation is not accurate anymore, the ROI should be 6-8 months in this case, and after ROI, your rig may take additional 12-16 months to get another $2500 if the price of ETH does not go up.
Situation 3, the worst one: BTC, ETH price going down, difficulty still going up (cause people already invested in the equipment so they have to use it anyway), at this case you may expect around 15 months ROI, or maybe never ROI, but good thing is your cards have resale value, so you can still sell it.
So the decision is yours, mining is fun, I must say that
, people tell others to not to invest to mining equipment but invest in the coin itself, that is also a good advice.
Let s talk about my situation, I bought 8 L3+ to mine Litecoin for their 2nd batch on 5 May, it costs me total 11 BTC = $13,200, including PSU and shipping charge, the BTC price is $1200 that time.
Now my 8 L3+ almost ROI, iti s about 80% ROI now
But the opportunity cost is pretty high, since 11 BTC = $30,250, BTC price is $2750 at the moment.
So do you think how long will my 8 L3+ earn me more $20,000 difference, considering more and more L3+ batch will come from Bitmain in the future? It is hard to say, but in term of investment, the decision to keep BTC instead of buying L3+ is a better decision.