When they re-establish contact with the mainland, you can use the gp limit of Sasserine (40,000 gp), but with a 6-month delay.
The population will be 450, if I remember it correctly.
And for a party with a caster capable of teleport or wind walk, such times will be substantially diminished. Renkrue's only about 750 miles from the northern edge of the Isle, perhaps 850 - 900 from Farshore, and easily within teleport range of 100 miles/level. Without having to sail all the way around the peninsula, Sasserine itself is at most 600 miles further as the crow flies. Wind walk wouldn't quite suffice to get you all the way to Renkrue at the initial casting level, of course, but using a rod of extend or a similar trick could easily get around that.
The only problem would be establishing safe stopovers in between. *grin*
It's just annoying to try to make the trip via Teleport dangerous. What would that accomplish? Just delay the party from actually progressing the plot or if it killed them, you'll have characters that got killed while going to the store. Random encounters aren't that fun.
In my Savage Tide, I allow them to get anything they want from Sasserine in 1 day (the time it takes the Wizard to Teleport to Sasserine and back)and refresh his spells).
Of course, if they Teleported out of/into dungeons, then I rolled the percentile chance of teleporting off mark, but in downtime, there's no point of bothering them that way.