I've had belt drive on my bike for two years now.
I thought I was logging all my rides, but I seem to have missed ten months out, so all I know is that I have done at least 6400km in that time; 2800km with the Rohloff and 3600km single speed.
I've broken three belts, then yesterday, I stripped a load of teeth off another one. (Apologies for the faulty camera focus)
I've also worn down two front aluminium pulleys. The rear steel ones seem to be lasting OK.
Cycle Monkey is the cheapest source for parts I have found
I use a 50t front pulley, with either a 118t belt and 22t Rohloff rear pulley, or a 122t belt and 28t SS rear sprocket.
The front pulley is about £50 and the belts are £55 or £64, depending on length.
Compare that with around £34 for a Renthal chainring and £11 for a KMC Z610 chain, which I was using before.
I haven't given up completely yet.
I've still got a brand new front pulley, one new of each belt and two part worn of each rear pulley, so I'll fit them and make an effort to keep track of how long they last.
Then I'll do the maths and try to work out which is the better option, in purely financial terms.
My guess at the moment is that at less than double the price, a front pulley will outlast two chainrings, so that's a good deal.
I'm not so sure about a belt at five times the price of a chain.
A Rohloff pully is £63, against £26 for a sprocket.
No price on Cycle Monkey for a rear SS pulley, but I would guess it's also about £60, against £12 for a SS sprocket.
I never kept proper track of chain and sprocket wear, but would two Rohloff and five SS sprockets last me two years ? I don't know.