I agree that's a bit bizarre!
As a comparison, we charge £320 for a fixed wing (PA28 etc) 50hr check (+parts and defect rectification). That we calculate as 8 hours work @ £40/hour.
Never really worked out why helicopter, avionics and twins cost more per hour than fixed wing single airframe/engine work!
Perhaps the 5hrs @ £50/hour = £400 is a result of someone leaving school before the maths lessons kicked in....?!