The former Republic of Ireland international is reported to be facing an uncertain future at Villa after making just 13 Premier League appearances last season.
Speculation has claimed that Boro have asked for first refusal on Ireland, but Mowbray has suggested wages could be an issue in any attempt to sign the 26-year-old
"I don't think there's anything to be said on that," Mowbray told The Gazette about a possible move for Ireland.
"I think you've got to put it in context. Stephen Ireland was at Manchester City not too long ago and he's with a Premier League club on a Premier League salary.
"I don't think he's gone on Villa's pre-season trip.
"I think with deals - whether it's Stephen Ireland or any Premier League player - clubs go through pre-season, assess their squads and then make decisions about footballers pretty late on."
The Championship club have also been linked with a bid to sign Napoli's Chile international forward Eduardo Vargas on a season-long loan.