2 observations here, pay attention to them.
This thread was created on June 12, 2019, today is June 26, 2019, so 14 days. Now, on June 12, eth was 242 usd, 14 days after that eth is 360 usd, so in 14 days eth had an increase of 118 usd which corresponds to almost 50% of 242 usd, so when I say buy eth is better than mine, you trolls must pay attention.
His post stated that he would roi in 6 months, so 50% is 3 months, pay attention that his earnings also increased too as eth values more but still a bit around 5 months and some days to roi.
Anyway, this is a very interesting observation.
This is what newbs fail to calculate. If the ROI interval shortens that means the coin is making good profits and even people with marginal electric rates will now jump in. That happens and the difficulty will go up. So while the fiat return may be the same or perhaps even better, the eth return is typically worse. The only time you can beat ETH returns with a rapidly rising coin is when you have a monopoly on specialized mining equipment. In this case granny is turning on her old PC to mine ETH and difficulty is shooting up.
It's hindsight, but better move would have been to buy ETH with the money spent on the 150 cards. OP will never make as much as he could have bought. NEVER. But if he/she has fun mining then who's to stop them. Just know it would have been better to buy than mine. This is true will all established coins in almost every scenario. Buying also affords you option to quickly exit the market should you decide you've had enough profit or loss - opportunity cost.