I don't think that you'll find the elements any cheaper anywhere else. They kinda keep the ball in their court with ba$tard sizing and limited distribution of the product. If you wanted to, and had a long enough lifespan, you could probably have a case or two worth of comparable filters made up by several manufacturers that make cotton wound cartriges. I did this when I wanted 3.5" 20" long media. It was a normal product that they produced ..but didn't have in inventory ..so I had to wait until they produced it. I imagine that the changing of a few settings on the machine that produced it would hav puked out anything that I wanted ..again in sufficient quantity to justify the run.
But seeing that many use ONE element for 15-20k ..and seeing that you may have to buy 50-100 elements, it's unlikely that you'll justify spending the money necessary to get them at a decent price ...when you'll spend less money in your lifetime just paying the ante that Oil Guard gets retail.
It's kinda a natural supply and demand road block that is in place here. Oil Guard is the only one with the type of demand that justifies such production of any economy.