I think in Liam's case he was not plugging Reason just for the cash. You can hear Reason through out his album - sadly. I really think Reason inspired him to get out a new album and for that he plugged it when it was brought up in interviews. Of course I'm sure he received a few chash bonuses for doing so too though.
In his case however, he obviously used it to the hilt on his latest, which indicates more than just a name drop cash-up scheme.