Unfortunetly they're not $5k, by the time you "upgrade" to the 90 HP version, and pay all the fees it's you're at $7k+ out the door. The "$4,995" that the seadoo marketing team has put out (brilliantly I might add) is not realistic.
On the topic of Seadoo Supercharger rebuilds, the first generation ('04-apx '08) need to be rebuilt every 100 hours or can destroy the motor, the newer ones need it ever 200 hours, a light on the dash will notify you. I once saw a pair of first generations that each had over 500 hours on the non rebuilt supercharger. As far as cost to rebuild, a dealer will charge $1,000+, if you pull the charger yourself and mail it off it's about $450.