What Mike said, plus it's $249 a month if you just buy one month (you have to commit to a year to get $199 a month) and only some contributors get 38 cents a download - it starts at 25 cents and increases as your earnings do.
Not every contributor makes it to the top earnings level (it's been a while since the sites had the stats that would let us see this, but the pyramid of contributors by portfolio size was very wide at the bottom, and similarly with total downloads per contributor; it could have changed over the last few years, but I doubt it).
Also, the downloads are 25 a day, so if you're a corporate user and you don't go in on Saturday and Sunday you've lost those 50 downloads - about 200 downloads fewer than the nominal maximum in a typical month. If you make a stab at the average sub download royalty at 32 cents x 550 downloads (750 - 200) that's $176 and SS keeps $73, about 30% of the gross.
I'd bet few subscribers download even 550 a month