My friend is still making $2 a day on each card but he has really low electricity prices. If you don't have cheap electricity you should sell all your gear and just buy the coins.
I assume your friends mining a pretty obscure coin, as even before electrical costs I dont see any cards breaking $2 per day on either Whattomine or Nicehash (even the Titan V on Nicehash doesnt break $1.50 daily before electrical costs). I still do agree that its better to simply buy coins right now, though, as mining at current rates isnt too profitable, and its risky to gamble on mining a low-difficulty coin and hoping prices go up on it.
Either that or another theory would be that your friend is lying or exaggerating about the amount earned.
Like leowonderful said, it is going to be extremely difficult to find a coin today that gives that amount of revenue. If anything, GPU mining is already unprofitable. The only course of action i see now is to sell GPUs and simply buy coins directly and wait for the uptrend.