We bought in Punta Cana - 2010, and I booked Riviera Maya for June 2011. I do NOT think this is a "scam" but you do need to choose wisely. I see prices that people have paid that are beyond my imagination - I paid only $2,000 US - so note that everything in life is negotiable.
I will find out in a month if I made a wise decision - it is true that since one is still paying the "inclusive fee" - how good a deal is it? I think it will work to my advantage; and that was negotiable too!
I am happy we bought what we did - but if you are buying for the transfers all over the world - then yes, it's just a timeshare - and ONLY if you are a good negotiator is it worthwhile....
Forewarned is forearmed - so buyer beware - negotiate or overpay..... I promise to write back after my stay and let you know.... waiting impatiently!