Spoken like a professional that actually researched the costs of materials, labour, insurance etc... and worked in the trade for years - no I thought not. Typical 'know it all' statement based in the hairy pimples on your buttocks.
You make it sound bad that the building trade has benefited...
Myself and a few of my mates in the building trade are busier now than years ago. The Olympics didnt affect us at all.
The estimate of £90-£100k is about right IMO.