Mahmood

Only you know what the hardware costs are. If you are buying whole sale, remember taxes and retail markup.
Again you know what you time is worth and you should be able to figure manhours.
It seems this projet is of new design and untested. You may want this customer to be the Beta test site. Cost savings to him. This would allow you to see what kind of headache you have created.
You should remember retailers will mark a product up by 50% to 100% (this is how sales can happen), so if your going to be the retailer take this into consideration. A market servey should be done to see the potintial sales of the product.
If you design the product with the customer in mind, and make it maintainable by him, by selling him spare parts, give traning, will reduce your long term effort.
Always consider change orders, normally this is a good way to makeup costing errors on new designs.

Please ignore spelling,
Good luck,
Joe