I'll give you a rough idea based on your info --
BWV (preferred), BCV and VWL all have the same point requirements for stays. OKW and BWV (standard) will be slightly less points.
Travel during Christmas Week (12/24-31) and the two weeks surrounding Easter each year fall into the most expensive category, Premiere. Thanksgiving, mid-February and the parts of March/April not near Easter are in the next step down, Magic Season.
A family of four could stay in a studio, like a deluxe resort hotel room with the addition of a kitchenette area (frig, microwave, coffeemaker, wet bar, toaster) or a one-bedroom which is quite luxurious and the real benefit of
DVC. You can also mix it up, using a studio some trips an one-bedroom others.
Sun-Thurs nights are less expensive than Fri-Sat nights. Some members make alternate plans for the weekends -- staying offsite or in a less expensive Disney hotel. Others just look at it as part of the cost. Do what works best for you.
Back to the basics -- Premiere Season the weekdays in a studio are 19 points and the weekends 43 or 181 points per week. A one-bedroom is 40/75 or 350 per week.
Magic Season runs 14/32 for the studio or 134 per week and the one bedroom is 30/60 or 270 per week.
150 points is the minimum purchase from Disney. You don't necessarily have to purchase the exact number of points you need because you can "borrow" and "bank" points. This would work if you went every other year and/or avoided some weekend nights.
150 points at $80 per point is $12,000. The yearly dues at BCV are currently $3.77 per point. You can figure it will stay roughly around this amount for at least the next few years. That would be a cost of $565.50 per year. You can pay it lump sum or over 12 months ($47.13 per month). The monthly cost for your initial purchase would depend on how much you put down, if you use a Magical Beginnings (sell back your first year of points), how long you finance, if you direct debit, etc., etc. Maybe a recent purchaser can give you a better idea of what the payments run.