So maybe all the hashpower entering the eth network is not just asics.
Given the profitability x return of investment, I'd say only idiots are buying and mining with gpus and yes there are too many idiots out there, I do not see anything wrong if somebody has a gpu and start mining cause maybe he did not mainly buy for mining so that is okay, now for somebody to actually pay $450 to earn $0.60 per day is unreasonable.
Also I said 80% of the hashrate from december 2017 - to right now are asics.
If there were ASIC miners for every coin I guess people would stop buying GPU's for mining. But sadly there isn't and people are left with only GPU as a choice. Also to say that someone is an idiot because s/he bought GPU for mining is wrong on so many ways, but I support your logic about price and income. Keep in mind that not everyone can buy ASIC miners, so for some GPU is easier choice. Also there are some features that GPU have which ASIC miners don't.