I agree with tvwalsh. It's not really cheaper; it's just different. Depends on what you want.
If you would actually have spent $800/night for a 2BR at BWV, then that's a fair comparison. But you've said that you have been staying in a single hotel room at a Disney deluxe hotel. Have you been paying discounted rates? Would this be your plan in the near future, if you don't buy DVC?
If so, that's the figure that you would compare with a DVC 2BR. Compare
your family's acceptable cash alternative vs. the DVC alternative. It doesn't really matter whether it's comparing apples to apples, precisely. What matters is looking at your costs and seeing whether the difference (if any) in buying DVC is worth it
to you!
DVC is not a cheap way to vacation. But for those who are not vacationing inexpensively anyway (Disney deluxe rooms are not cheap), it may be very worthwhile!
If you split up your points to spread a week's worth over 2 stays of 5 nights each, then you gain more nights but add the cost of two transportation days (airfare or car travel)! Again, perhaps not cheaper, just different. If you want an honest answer, by the numbers, compare fair numbers for your
own situation.
Then consider the intangible benefits and disadvantages of DVC/timeshare, depending on how
you see them:
--- upgrade to a 2BR - fantastic!
--- loss of housekeeping - do you care?
--- upfront payment - ties up your money or prepays vacations?
--- long term commitment - limits your options or encourages needed vacationing?
Some people love all the great DVC resorts. Some miss the theme or location of their favorite non-DVC resorts. There are so many intangibles - it's hard for other people, whose priorities may be different from yours, to judge for you. Even the various ways of making financial comparisons will come up with different responses to your question about breaking even.
Maybe by seeing the variety of responses here, you can choose the best approach for you and decide for yourself.

HTH!
