Barry and Milner both earned sizeable increases in their salary when making the move to Manchester City in ?12million and ?24million deals, respectively, in the pre-Houllier era.
Villa are bracing themselves for a similar battle to hold onto Ashley Young this summer with the England player being linked with the two Manchester clubs, Liverpool and Chelsea.
Houllier believes in general that a player has to weigh up the worth of giving up the chance to play regular football - at Villa - for extra financial riches elsewhere.
But when asked about the departure of Milner and Barry, Houllier said: "If sometimes, if you ask some players would they like to be one year younger, I think they would take it and consider things differently.
"Money doesn't buy you a regular place in the team and what players have to do is to think about it. You want to play. A real player has got the desire for winning and also a love for the game and wants to play."
Source: PA
Source: PA