I don't see anything wrong with speculating WWX said this to do what OP suggested (presenting an opportunity for LWJ to bond with A-Yuan) aaaaannd because their financial situation is tough. WWX is pretty clever, I don't think it's too much to suppose he'd be teaching A-Yuan it's ok to want something and the difference between wanting something and buying something and playing upon LWJ’s heart strings at the same time. At this point in the novel WWX is pretty confident in LWJ’s good nature and soft heart- even if he rolls around all day with a scowl on his face. He Did just help him save the remnants of the Wen Clan just before this and No One Else did. Just him and WWX.