Money is important (indeed it makes the world go round). Its a short career, his and his children's future,
I think that argument is more compelling when talking about somebody like Grant Holt grabbing an extra year at Wigan, after finding himself in League 2 at the age of 27, rather than a 26 year old who has likely received about £1.5m in signing on fees alone (10% of transfer fees is typical?), would stand to gain another £350k signing on fee from this deal, and is probably on something like £1m a year, he's almost definitely already a multi-millionaire and probably already made for life if he's got his head screwed on.
Although I think he's just playing a long game with Lisbon to squeeze a bit more out of them, or using delaying tactics in the hope that somebody else puts a better offer on the table at the 11th hour, or forcing our hand so that we make him a settlement offer to make up the shortfall with a lump sum. Or rather, his agent is advising him to do that, must remember that his 10% man won't want to take a pay cut either.
I doubt he'd choose becoming the new Becchio and playing with Norwich U21's for the sake of a few grand, although he may be thinking that he could go out on loan again and we'd have to make up any shortfall.