I have an electric shaver. I've used it as long as I can remember. The cutter and foil need replacing now, and that costs $75 (yes, even on eBay). They recommend you replace those parts every 18 months, which comes out to about $4.15 per month. And if you manage to double the cutter and foil lifespan, as I did, you'll only spend $2.08 per month. If you buy a pack of good disposable razors once a month, that will probably cost you about $10. I'm ignoring shaving cream and aftershave. So the cutter and foil starts to look pretty good.
But here's where things get silly. You can buy a whole new electric razor for $50, and if that lasts you three years, you'll only be spending $1.35 per month, until you have to replace the whole thing again. So the cheapest option of all is to treat your entire electric shaver as disposable and just buy a new one when its parts wear out. And that is a demonstration of how our world generates such prodigious waste. We have optimised our manufacturing for brand new products, not repairs.
Mokalus of Borg
PS - I have started using disposable razors.
PPS - At least until I can justify replacing my electric shaver.