There two reasons cars are generally more expensive in Puerto Rico. 1st is the double-shipping (though not all manufacturer's suffer from this). 2nd, and biggest, is the Excise Tax that is applied to every car brought into Puerto Rico. This tax is based on the value of the car (new or used) and runs around 15%-18%. Good news, the smart qualifies for the LOWEST rate (actually 14.5%) of any car imported. For example, a Passion starting at $13,590 would have a $1,959 excise tax, for a
PR starting price of $15,549. (source
Departamento de Hacienda de Puerto Rico)
So the prices you are are hearing that Royal Motors will be charging for the smart car are probably appropriate.
You can go buy one in the U.S., then drive it around for 6 months so it becomes "used" and then ship it to P.R. (around $800-1,200). You will still owe 14.5%, but it will be on a slightly reduced used value. Not really a great trade-off I think, as the smart probably doesn't drop much in value after 6 months.
BTW, I know this because my father worked for the P.R. government while I was growing up and he helped re-write the auto Excise law to both lower it and make it so it treated cars of any size/power fairly (it used to be higher and tax above a certain weight and horsepower differently too). This was back in 1992.