Those Billboard rules are only for the first 4 weeks of an album's release. Anything after 4 weeks, very low prices for albums will be tracked into Soundscan's system.
Uh oh. I could see this catching on. Labels will wait until the 5th week to discount the album to a couple of pennies in hopes of breaking a record. The sad thing is that people are using what would be a good deal for all the wrong reasons. I'm all for making digital albums much cheaper than they currently are, but don't do it to compete with another website or break a meaningless record.