Maybe its beacue I only ever buy budget stuff.
Shimano R-550 wheels for £100, compared to the the mavic CXP/basic shimano hubs they replaced there's no comparison, especialy as I got them for a bargain £35 posted!
They'r my one and only wheels, never let me down, bearings greased once a year. And anyone who has ridden in the peaks (I'm thinking decending form Crookes down Manchester road to ladybower) will know the benifit of comfortable wheels at 25mph, its a horrific surface! They've even taken a beeting on the odd excursion off-road on smooth singletrack whilst touring.
An open pro rim and 32 spokes costs almost as much as a budget factory wheel, and at/over £300 you'r just throwing money at the hub, at least factory wheels shed some weight form the rim/spokes where it arguably makes more difference.
If I wanted £150 traing wheels I'd look at hand built, otherwise budget factory ones are cheeper, or expensive factory ones are lighter.