Since there are all of 2 tuxedo rental places on the island of Kauai we didn't have much of an option. Robert's conveniently has 2 locations - one in Lihue (the main city) and one in Hanapepe (west). They do not have a website, which is kind of...
a pain so you have to either go in (convenient if you're on island not so much if you're planning from afar) or you have to call to get their email address and communicate with the owner.
Their selection of tuxedos is pretty good for such a small island but the majority of the tuxes are flown in from the mainland, which adds to the prices. There are several fees involved that seems tedious such as a small order fee, etc., which I wasn't happy about but again didn't have much of an option.
When it was all said and done our the tuxedos cost about $215 EACH to rent for a day. Since my fiance is very large in the arms and chest and small in the waist we found his tux would need quite a few alterations, which they could not do since it was a rental. I found a place online that sold the same tuxedo for about $75 more to purchase than it cost to rent it. Needless to say, I purchased it.
Overall, the service was alright. The owner takes too long to respond to your emails and the tuxes were extremely overpriced.