What do you expect from the industry that pioneered "throw-away" marketing?
Even at the turn of the 20th century, King C. Gillette was all about handing the consumer a blade for next-to-nothing (perhaps even less than his actual cost) in order to get an eventual return on the marked up replacement cartridges.
Since then, other industries have followed suit... Some media boxes, gaming platforms, printers, etc.... all might actually sell at a loss on the idea that you'll be back for the "cartridges."
Even freebie email accounts and other internet services can be said to be following this form of marketing strategy, as they put the product up at no cost, and make their money on advertising down the road.
Back to the razors... perhaps unlike you, Sarah, I am a bit tight with money, but I've already considered the math, and think they're worth it.
I use a Gillette Fusion, myself.... and, yeah - the blades are expensive, but they last for 2 months+, and you can't really get a smoother shave... can whip right through it - no cuts or anything... and, with that quality of shave, I'm willing to pay 7 cents a session.
Hell... the time they save me, alone, is worth that, I think.