One thing to look at is how high you have the Reefmat mounted out of the water. I moved mine up about 3" (i.e. the water level down 3") and the added water pressure improved efficiency by 2/3. I was using 30"/day, now about 10".I use 1 red sea reefmat 1200 on my 340 gallon display 75 gallon sump with a skimmer rated for 300-400 gallons at high bioload 500 gallons at low bioload, and an Algae turf scrubber, plus a cannister filter filled with matrix rock and a pellet reactor both for denitrification. That said, with all that. my phosphates still test out at between .05 and .15 ppm (weekly) and nitrates have tested at 20.5 ppm (weekly).
I go through approximately 80 - 100 Inches per day (Around 7 to 8 ft per day). Which lasts up to 15 days for me per roll.
At $60 a month I can buy a lot of filter socks. The rolls come out solid brown in color and I feel like my skimmer's job has been reduced to oxygenating the water. If anything I wish there was options around 200 micron or 500 micron to allow the skimmer some stuff to skim out. But, that said, I am no where near bottoming out nutrients. I'm hoping the roller mat doesn't need as much paper the longer it goes, but, seems to be a consistent thing month over month right now. been running it at this pace for about 6 months.