I'm quite pleased to report that the Generic Value Products version PM SS Serum is very similar to the original. Possibly, the only difference I've seen is that the generic makes my hair dry VERY fast. This might be good or bad we'll see.
The generic is sold at Sally Beauty Supply at 6 ounces for $8.99, with the member card it's $7.99
I buy the Paul Mitchell version at Ulta with a $3.50 coupon. Ulta doesn't have prices online, but I'll update this post once I stop in there.