Testing a 40% price bump on new clients only

I'm not raising prices on anyone already on my books — that's a different experiment and I don't want to run both at once. For the next month every new enquiry gets quoted at 40% above my current rate, nothing else changes. Ten enquiries is the sample; if eight or more say yes without haggling I'll make it permanent, if they all vanish I'll know I was already at the ceiling.