Once an artist reaches 30k Amazon will invest $1,000 into that artist (2 artists were invested into within minutes of the deal being finalized) Also once the same artist reaches 35k Amazon will send out mailers to people who have bought music that sounds like that band. I am sure beyond that amazon will do promotions as it normally does through the community review process more reviews the better the search results.

1st correction is that SAB is not like a bank. In fact according to German law they have to use a notary along with an escrow account. I mention that here http://blog.timelineonline.org/2007/11/sellabands-escrow-account.html

The 60% you refer to is publishing which is different then the album sales to which artists only get 1/3 while the fans also get 1/3 along with 1/3 of the advertising you mentioned. This is part of fans and artists working together.

Then a final word 2 artists as of 10:00 a.m. PST had 100 parts bought by amazon.co.uk with each part costing $10 that is $1,000 each for Bullet Proof Monk and Solidtube.