I have bought some off brand trac2 cartridges from StopnShop(US supermarket) that shaved just as good as anything else I have used and were $2.50 for 10 cartridges. I mean there are cheaper alternatives out there if people are willing to look and try them. For example you can get a 100 Personna trac2 cartridges for about 17 dollars online.I agree with your 2nd paragraph.
Trac II carts sell for about 2 bucks per refill cart.
That's 20 times the cost of my DE blade, so I can't agree they aren't expensive.
There are carts cheaper than Fusion, but overall, they are still vastly more expensive than DE blades.