Interesting thoughts, but I think you're a little off-base in your reasoning. The only time that Disney profits on a cash reservation is when a member has used his/her points to trade-out of the 7 DVC resorts. Disney converts those points to cash rooms which are rented to the general public, and pockets the proceeds.
Any other time, proceeds from cash bookings are returned to members. It's listed in the annual budget as "breakage" income.
The primary reason for the higher point weekends is to balance demand. If the point schedule was flat, weekends would be booked solid rather quickly by members within driving distance of WDW who want to stay over a long weekend. Many seem to think that the weekends currently do cost too much in comparison to the weekdays, but that's a debate for another thread.