Later in 2017 early 2018, it was the same story with the RX 4xx/5xx GPUs, they cost like $250 CAD and you made like $5/day/gpu with them, so your ROI was 50 days.
Now the ROI times are crazy high and I think most people are either betting on the fact that ETH goes to $10K or that their $1000 GPU will depreciate slower than their revenue. However nobody knows what top ETH will hit and who knows how much these GPUs are going to be worth when ETH goes POS sometime in the future.
Now is not the best time to start mining really.
I think what most people are doing is buying the equipment first and doing research after. Most people I know who asked about Crypto I told them, that you can buy the GPUs it will take maybe 6-9 months to get ROI on the GPUs and most people don't like that timeframe and they invest their money elsewhere.
I know many people who bought some GPUs, wanted to mine Bitcoin with it, and then they realized that you couldn't mine BTC with GPUs anymore. So I told them to mine ETH and they were upset that they only make like $2/day. They were expecting to make like $100,000 because after all "Crypto is a get rich quick scheme".