The other poster here is mostly correct. These are essential to a 6hit build (you sacrifice the least by using these) and have only one strength less than Rutter Sabatons. The HQ have the same strength, which explains the demand and the price. Usukane feet are really the only upgrade to keep a 6hit build, as those combine the best of Saotome Sune-Ate, Fuma Sune-Ate, and Hachiman Sune-Ate all in one piece of footwear.
At 70 you get +25 store TP through job traits. This can be merited to +35, and from there you need +11, not +15 (for your typical 450 delay GK) to hit a 6 hit build.
Bear in mind you'll need more store TP for TPing in if you macro out Store TP gears for your WS!
A 6 hit build requires 11 STP. I have 2 setups that I use depending on the situation. I use Askar Body and Fumas when acc is close to cap. I use Haub and Hachi feet when I need more acc. Both sets yield the 6 hit build with the 6 STP from Rajas and brutal.