For the price of a normal 6 Star, 60$, you're getting:
14 units between 3-6 Stars at normal rates, or, under the best of circumstances, 3 100 Nutaku gold Single pulls and a 50FG roll.
A Rainbow Skillbloom, don't know if these have ever been priced in the shop but are reasonably in short supply at a limit of 1 per month.
A Rainbow Dressbloom, previously priced at 50FGs, or the equivalent of another 50FG roll.
And a 15th unit of Rainbow rarity, normally a 60$ price tag alone.

I doubt anyone actually buys FGs to roll 10+1s but if they did it'd be around, what, 50 bucks a pop?

The deal is great for anyone who's willing to spend that much. If you're not someone who intended to purchase outside of Black Friday/Easter level deals, or a player without Rainbow units, going past stage two is probably not worth it.