A half decent chainring could easily be costing you upwards of £50, a cog £10-20, I'd expect a cheap KMC chain to be completely unusable before the year was out so lets say £20 for a chain. So a conservative £80 - 90 a year as opposed to 4 or 5 x £5 for a KMC 510 every few months = £20-25. So almost 1/4 the cost plus you have a drivetrain that works, smoothly, doesn't drop chains and doesn't fail at some unknown point putting you over the bars or worse.
A year from a chainring and cog is bollocks.
A half decent chainring could easily be costing you upwards of £50, a cog £10-20, I'd expect a cheap KMC chain to be completely unusable before the year was out so lets say £20 for a chain. So a conservative £80 - 90 a year as opposed to 4 or 5 x £5 for a KMC 510 every few months = £20-25. So almost 1/4 the cost plus you have a drivetrain that works, smoothly, doesn't drop chains and doesn't fail at some unknown point putting you over the bars or worse.