@oristarA,
"So much for" is basically inferring that the original promise had come to nothing.
The Government promises to have a bonfire of the Quangos, meaning that they will split them up and get rid of as many as possible because of their cost, and lack of effectiveness.
One year later and it is found that they have even more than they started with.
Sarcastically, one would say "So much for
that promise" , meaning that, in the end, the promise was worth nothing.
I went on a chocolate and beer diet to lose weight, and gained ten pounds.
"So much for
that diet!