The 23-year old has emerged as a January target for Rangers but Lomas, who oversaw his first Scottish Premier League match as boss with a scoreless draw at Ibrox on Saturday, has priced him at over £1million.
"I've already got the handcuffs out for Murray. He's a fantastic player and we saw at Ibrox what he's all about,” Lomas said.
"He got forward and into the box throughout and showed what a fantastic athlete he is. If we're to kick on we need to try and keep players like him.
"I know Rangers tried to sign him in the summer and Murray is good enough, but if we're talking about him moving on it'll need to be one helluva an offer.
"He's definitely worth over a million quid, for me.
"I've already said to Murray he can be as good as he wants to be. He gets in the box and into so many scoring opportunities, and goalscoring midfielders are hard to come by.
"I've watched him before coming to St Johnstone and liked him, but now I've worked him I'm even more impressed."