Given it is between 500 to 600 for access to the isle (Amulet of Loblobliiiblop), and another 300 every time you set spawn point to the isle, I thought it might be fair for those with both (spawn point + amulet) to get free resting in the Shallow End tavern, given you've already paid the equivalent of 53-60 rests. Certainly helps to offset the cost of boating, at least, if you live there. At worst, the prices could always be upped a little bit to make up for the resting, as well.
I don't think they like lung-breathers hanging around in their inn very much.