Interviewed in Poland's Super Express newspaper, Grant admitted: "Boruc's performances (in Euro 2008) were no surprise because I knew about him from the Scottish league.
"I wanted to take him to Stamford Bridge and did an overview to check how much we would have to pay. But it appeared that Celtic expected a huge amount of money.
"Now the price tag is unreal. When I hear that, after a strong performance at Euro 2008, he is now worth between £10m and £15m, I know immediately that nobody will pay that kind of money for a goalkeeper.
"Boruc is a top-quality goalkeeper. He is brave, confident and he won't get scared by anybody. Having a goalkeeper like this means you are midway to success.
"But I repeat, these kind of amounts are not paid for a goalkeeper - I think he will stay in Scotland next season."