I believe that the best investment for maintaining the status SFI every month, may be purchasing TCredit Pak (125 TCredits) - Special Standing Order only, $ 36.25.
In this way you have 1500 VersaPoints to maintain your EA level, then you can participate in the auction and even if you do not win anything each Auction BIT is converted to 1 Member Reward Point (MRB) so you can use MRB to get discount for other TripleClicks purchases .... better than that you can not!