In the days when I was young, firm and fruity and treated my b00bs with respect, I used to spend that sort of money on Rigby & Peller bras, got fitted there too. They were worth every single penny, I hand-washed them lovingly and they lasted forever. They lift, hold, shape, define, reduce, flaunt, thrust, whatever you need. Have no idea about the quality of the Spanx ones but they seem like a generic squashing device, not the wonder of engineering and corsetry covered in silk, lace and embroidery that I remember dimly from my wage-earning, single, past.
I miss being fruity.