FWIW, I don't think it matters how much you spend, I paid £75 for a
Polar CS200CAD, the bl**dy thing will insist on giving me random cadence readings. The cadence meter isn't even fitted to the bike!!! I emailed Polar 4 times to ask about the fault and to see about getting it replaced under warranty (it was only 7 months old) when the problems first started. They never responded, bunch of b*st*rds. I'll never buy another Polar Product again, crap after sales IMO.