My quick Google search pegs the increase in starting salary going from BS to MS at $18,200 a year [1]. Being able to make that leap for $7k seems like a pretty good deal to me.
[1] http://www.naceweb.org/Press/Releases/Payoff_for_Master_s_De...
PhD admissions are highly selective, and terminal MS programs are highly expensive. The Master's degree means you were either a top student (able to pass PhD admissions) or independently wealthy and probably packing serious connections.
When it no longer means that, is it still going to provide the salary bump? Quite possibly, yes. I wouldn't call it guaranteed, though.
It will be interesting to see how the market reacts to this degree. Will it be regarded as a masters degree from a top 10 program, or will it be seen as a cheap online degree that doesn't hold the same esteem?