Laundress
It's a hole in how-to-run-your-business. First, 300+G washers cost 2-3x more to purchase than the 90G hardmounts, so most owners won't spring for them when they are already cash strapped going into business. Second, by increasing extraction, you loose time (read: money) from your dryers. Owners who do have hi-extract washers are still trying to figure out their pricing balance so as not to piss people off (charge more for washers? decrease temps in the dryers? 2 minutes/quarter? etc)...
Believe me, when the Neptune first came out, I asked all manufacturers when they would come out with a commercial grade 300G washers, at which they promptly laughed. Why would anyone want them? You will spend all your money and no one will use them. You won't make any money in your dryers. No, settle for the status quo...
The hot thing now is 200G hardmount washers. All manufactures have them now at a modest price point up from the 90G machines. All the manufacturers will also tell you that when you look at the amount of water extracted over time, the jump from a 90G machine to a 200G machine is remarkable, but a 200G compared to a 300G machine is very minor. I haven't seen nor looked for this data firsthand... Then they will tell you that the way a typical laundromat user uses coin-op machines, 300G machines rarely get balanced and achieve full speed.