When you buy into the program, you will pay a fixed dollar amount per point--about $95 per point direct through
DVC or more in the $65-75 range if you purchase a resale contract.
That will entitle you to the allotment of points (200 in your example) every year through the end of the contract. Contracts at OKW, VB, HHI, BWV, BCV and VWL end in 2042. Contracts at Saratoga Springs run through 2054 (which is most of the reason why it costs more to buy direct from DVC.)
The only annual costs are maintenance fees (aka annual dues). These will vary depending on the resort you own, but $4 is about average. SSR is $3.80 per point, while other properties are higher or lower.
Thus on 200 pts, you annual fees are about $800 per calendar year.
The dues figure is updated annually, and is directly tied to the operating costs for the resort you own. In this respect, DVC is a non-profit, so they cannot arbitrarily change the dues to any figure of their liking.