It was basically explained like any other annuity. You put in $$ up front, the company invests the $ and they make their money over time. Then they pay what was promised and they keep any extra profits. I mean, $10,000 over 25 years with compounding interest, is probably $40,000 at 5 or 6% and I am sure that they aren't just watching it compound, they are actively investing and trading. I did not buy the annuity from the timeshare salesperson, I inquired as to how they make money. The first answer was "Investing over time and trades" the second answer was "Breakage". Breakage was people who sell their timeshare, give it up, don't pay maintenance etc, etc.
It is pretty rare that someone keeps their timeshare for the whole 25 years.