B&T USA is going under after B&T won the lawsuit. It’s going to take a while to get B&T products back in the US.
4.6mm the last time I checked was somewhere between $0.50 to $0.60 a round for FMJ target ammo. 5.7mm is a pain because factory made rounds to FN specs use a glued bullet and has to be coated with a dry lubricant that isn’t cheap. As far as I know 4.6mm doesn’t have that problem but just has terrible ballistics out of a hand gun.
That said, because no real pistol of a 4.6mm exists, the AP ammo could be considered a “non-pistol” round as long as the civilian versions are SBRs. Food for thought.
Though the correct take on this is bout 4.6 and 5.7 are memes and backpack PDW larpers should stick to H&K SP5s.