The Northern Ireland international is reported to be generating interest from across Europe after reigniting his career in Scotland.
Having started on the books of Leicester City, McKay spent two years with Northampton Town before heading north.
The 24-year-old forward has become a key figure for Inverness, netting 27 times in all competitions last season and nine already this term.
Butcher is aware that such talent will draw admiring glances, but has made it clear that Caley will not allow their star striker to leave on the cheap.
He said in the Scotsman: "(Billy) is much admired by other managers in the league but it would take a really special fee to get him.
"Billy is almost the perfect attacker and he will cost a lot of money."