Fletcher completed his move from Burnley for a fee in excess of £6.5million on Thursday but McCarthy pays little attention to transfer fees.
He sees the signing - and that of Jelle Van Damme, who cost around £2.5million - as a sign of Wolves' ambition but is more concerned with the attributes of his new players than their price tags.
"The money side of it doesn't bother me," McCarthy told the Birmingham Mail. "It's the player, the personality and the character that he is. Steven will fit in here perfectly and I'm delighted to have signed him.
"We've got a budget which we work to here. We did it last year getting 'Doyler' signed up early when he was the primary target. We'd been trying to do Jelle Van Damme for quite a while and now Steven.
"It makes us a better squad already with two very good players."
McCarthy is planning further forays into the transfer market this summer and will now sit down with the club's owner and chief executive to decide on his next targets.
"I'm really pleased to have got two done as early as we have done like we did last year. But we're still looking for more and still looking to improve.
"It's something that myself, Jez (Moxey) and Steve (Morgan) sat down and spoke about and said we were going to spend in the best way that we could to improve the team. We've already done that with Jelle and Steven and we'll continue to look."