Herves margin numbers are about right - I used to be an auditor (not Andersens before you ask, another big 5) and so I used to look at Gross Margins all day long.
Here are some figures that I have briefly put together based upon the UK:
Single Owner shop, wants to gross £40k a year.
Ougoings (all figures per annum)
=======
1. Employee costs: £40k, plus other taxes = £48,000 total cost to business.
2. Rent of Shop - say £12k
3. Rates (local taxes): £500
4. other bills: £500
5. Other costs (stationery, advertising, accountants, etc.): £4k
Total Fixed Outgoings: £65k.
If each computer retails at £1500, then that means the revenue to the business is (£1500 / 1.175) = £1275 because it is necessary to charge VAT on the goods (he is making enough revenue to demand that one). Assuming a gross margin of 50% then the contribution (profit) associated with each computer is (£1275 / 2) = £638.
This means that the shop must sell (£65,000 / £638) = 101 computers a year. That is two a week, which I don't think is unreasonable. A couple of large deals to local offices would set the owner up nicely for the year.
You can plug in your own numbers if you don't agree with them - but these are quite close for the UK, though there will be startup costs involved and maybe some other small costs.
Roger.