Then they should not come out and say they've moved for progession then.
IMO it depends, you could argue that the biggest reason is money but progression is something that can be accomplished too with the movement, depending on the club's ambitions and goals.
Take Ashley Cole moving from Arsenal to Chelsea as an example: At first you would say that he's a "mercenary" and money talks, which is indeed true. But when you have a look at the trophies he's won with Chelsea and the trophies Arsenal has won in the same time span you can say that he also progressed career wise.
If it was a move to Al Ahli or some asian league team, yes it would be entirely for the money, but i fail to see how they won't achieve progression as a part of the move granted they're still playing high level football and have team mates of a similar level of the players in question.