In reply to Scarab9:
From a business owners perspective, I think you are probably underestimating the 'costs' / overheads. Sure, as an in-going concern/project the costs are probably as you describe and they are making good money out of you. However :
They need to win the project in the first place. They've probably paid for marketing/directors meetings/contract drawing up etc. prior to it going live.
Not every project is a winner, or even won. The costs above may be incurred and there be no return.
There are dozens of fees and taxes hidden away in overheads. Obvious ones like corporation tax, business rates. Then loads of others. Insurance for cars, employers liability, public liability, professional indemnity, product liability, contents, buildings, business interruption and probably more. Water, electricity and gas/AC. Telephones can cost a fortune, particular with rented systems. Mobile phones. Building rents and maintenance changes. You have to pay for the space that doesn't make money - canteens and toilets etc. Health and Safety might not be a massive issue, but they probably still pay a consultant, fire risk assessments, fire extinguisher servicing. Trained a first aider? That's 4 days salary before the cost of the course. Then it needs renewing and someone else trained for holiday cover. Do they have a defib? That's a grand alone. Software costs? Licensing done properly is expensive particularly with specialist stuff. Membership of professional bodies and the quangos that tag on to all medium businesses . Chamber of commerce, fsb, cbi, trade bodies etc.
Employee costs as highlighted above can be quite high. Employers NI, sick pay, holiday pay, company cars (for some), uniforms/ppe.
Then there is risk. Suppliers go must and it costs to fund an alternative. Customers go bust and never pay. Projects get priced wrong - not surprisingly these are the ones you are most likely to win!
An finally, half of the folks are probably unproductive lazy arses and they have to pay them too.