After reading the Alu to carbon mast thread, is it worth the cost, I decided to do an unscientific test to demonstrate the differences in carbon masts. I suspect any low end carbon mast would be marginally better than a high end alloy mast but I can't verify that.
I have four 95cm carbon masts and measured the deflection of them using a large concrete block balanced in the middle. Probably 40-50kg.

I am not bagging any brand as I have had many happy hours and done hundreds if not a couple of thousand km on the worst of them in this experiment and until you try a stiffer mast you don't know any different any way. Also being the most used by far, it may have lost a bit of stiffness from new.
Original starboard carbon, 13mm deflection.
NP F4 Evo 9mm
Patrik standard carbon, 7mm
Patrik HM carbon, 3mm
With my 100kg hanging off the side of a 91 board and a 900 race wing this makes a massive difference to the feel of the foil for the better. Freefoiling on a narrower board especially with a lighter rider would be less noticeable.
My advice would be to go for the stiffest mast you can afford or in these covid days, that is available.
If foiling is your thing the cost is worth it, if you are an occasional foiler, probably not.

Wouldn't it be nice for us consumers for there to be a standard for foil mast stiffness. Unless you believe all the brochure speel the only comparison available to most of us is standing on your mates mast with one end on the kerb.
Happy foiling peep's, no matter how stiff your mast is.