It is quite difficult to find a rank seller who is buying the more expensive ranks especially if one is not in an USA time zone when player activity peaks. eg, finding someone who is spending $80 +.Consequently I am sure some players give up on try to rank up.
A solution is to have a web/forum based meep account, where players can save $ credits that they have exchanged for meeples. Then they can do a deal with 4 different rank sellers for $ 20 and when the last deal is done, buy the rank with the $80 on their meep account.
I believe this would result in more donations as players would encourage more donations or purchase part of it themselves.