my take on it goes something like this:
I never advertise a teleport service... therefore I have the right to refuse regardless of if I have the spell or not.
I quite recently did manage to farm enough gil for tele-mea cause the Necropolis is a death trap and a 1/2 (lost a lot of xp that day)... I've been busy farming to make up for the sheer gil loss of buying the teleport scrolls (Mea - 60k, Holla - 35k, Dem 7k, over 100,000 gil spent on scrolls).. so usually I'm REALLY busy... I farmed for the spells alone, couldn't find any help doing the quest... so I see them as "my" spells, to do with as I please.
so I simply tell people that I'm busy right now.....
typically the respons is, "ok".. a more *interesting* respons was "are you sure?" which I replied.. "Positive"
see, unless I'm offered a SEVERLY high amount of gil for the port.. there's no way it can out-do how much I can make farming.. and since I don't advertised teleport service, it means I have the right to refuse... Add to that there are MORE than enough people in each city offering a teleport service.