Ok it is true that you pay slightly less in MF per Point the more Points you own but of course the gross MF would increase. Also remember the MF are in 2,500 Points increments. Many years ago when we were about to go to 63,000 Points it was pointed out that 65,000 Points paid the same MF as 63,000 Points. So while the outlay for those extra 2,000 Points was slightly higher the MF did not increase. So it is always best to be near the top of the bracket.
As for buying 1 time use Points from other Worldmark Members that is a very economic way to go. The 1 time use Points cost from 5.5 cents to 7.5 cents with no ongoing obligation for the MF of those Points.
When MF are set they are based upon your total Points - whether resell or Developer Points or a combination. We have stopped buying Developer Points. Our last 2 additions were resell purchases combined into our regular account.
Also buying Developer Points now to get to a Travelshare Level that does not exist will not get you to that new level once it is announced. Only Developer Points purchased after the new level is announced will count towards that level.