I think it's just random.
My turnip prices are normally low, but they were once 650 and I got a lot of money from tips *v*
It turns your turnips rotten.
Does time travelling mess with your turnip prices in this installation? In CF, if I remember correctly, if a "time paradox" was detected, it would lower turnip prices significantly.
I don't think so. During my TT once I got my turnip price to be 524 bells.