There won't be just one team interested and it depends how much a club can afford to take a gamble. I wouldn't sell him for less than 7 figures with another sell-on clause.
ML is an asset and I think poacher instincts translate better through the leagues than say a good lower-level target man so I'd quote £2/3 mil if championship clubs come sniffing. If his 40+ NL goals translate to 15/20 goals in the championship then that could be the difference between a £150m windfall for that team or not.
I'm sure a championship team won't want to potentially miss out on the next Vardy for the sake of a few hundred grand with what they could potentially gain through future revenue if he's a success at his next club.
I'd be utterly amazed if we see him again after May.