It’s not a good exchange rate because you could go to any one of the rental sites and get $14-15 dollars per DVC point vs using them directly through Disney to exchange into a cruise where they only give the points about $8.50 value. You could rent out half the amount of DVC points and pay cash for your cruise vs using double the amount of DVC points to book the cruise through MS. If you need to cancel your cruise those points also can only be used as Disney collection points and can no longer be used to book regular DVC rooms only other non- DVC Disney resorts which also do not have a favorable exchange rate.