The only good point is that it's on dimensionally stable polyester base. The bad news is that its awfully high contrast, you're on your own trying to figure out how to tame it, it's rather thin for masking purposes, you're going to have to buy an awful lot of it at a time if you can even find it, and it requires special processing. I don't see any way your can save money that way!
As far as Fomapan 100 goes, I think you'll discover it's somewhat too grainy to be ideal for small format film masking. Its only benefit is its lower price point. Only the sheet film version is on polyester base. But you wouldn't want to use any kind of roll film for masking anyway; it needs to lay completely flat.
Yeah ... the price of all brands of sheet film has gone up a lot recently, but so has everything else. But if you're only masking small originals like 120 you could cut sheets of 4x5 in half in the dark for masking usage. That would save you money.