[Valgrim]

I agree. My personal experience is that the chain and derailleur are by far the most fragile parts of the system (disk brakes are probably quite fragile too, but regular caliper/cantilever/v-brakes are not much affected by corrosion.) but on cheap bikes, chains are easy to replace and derailleurs have a lot of tolerance. So just cleaning them regularly and oiling them is generally good enough.

Some specialized winter bikes use a belt instead of a chain, but I find those too expensive, hard to service and maintain.