Are the mugs collectable?
Not especially, there are thousands in circulation, but since the Pussers website is not listing them currently no doubt a redesigned version is in the works. But your price is very reasonable (and shipping) for someone that wants one of this pattern, no doubt if you hang onto it for a couple of years it might fetch a little more. Good luck with the sale.
If you want to collect, I think the decanters, esp the small ones make nice ornaments.
British Navy Pusser's Rum Small Hand Crafted Porcelain Decanter with Contents. | eBay
Les's official stone flagon with issue rum however, could fetch a tidy sum. When a batch turned up in Dryad (IIRC) in the mid 90's, they went for a couple of hundred apiece. They are getting fewer by the year, a real heirloom to treasure.