Let's do this quote online, group effort. I suggest you take several online estimates and key them into a spreadsheet and average them out.

Lets start by listing expected hardware expenses:

HARDWARE:
1). 8051 project board with ADC ports
2). Special I/O boards for analog conversion
3). LCD display module
4). Power Supply
5). Metal Case / Polycarbonate is easier
6). Bezel for display fitting to case
7). Machine work to case
8). Wiring to client's equipment
9). Special connectors

HARDWARE: ROUGH PRICE ESTIMATES:
1). $250 to $400
2). $30 to $60
3). $20 to $30
4). $15 to $30
5). $20 to $80(large metal)
6). $5 to $15
7). $5 to $40(metal)
8). $15 to $15
9). $15 to $15

This estimate gives me the following expectations:

Low: $375
Average: $530
High: $685

At this point I'd call the customer and see if a polycarbonate (plastic) case is acceptable since its the biggest price varient. Using this allows easier drilling and cutting to mount the electronics and the display bezel. however, the power supply will probably be heavy and so the case will need to have room for it to sit at the bottom. Getting a small power supply would be important. Would they accept a plug in electronics transformers adapter like we see in the office? Maybe. It would allow the case to be smaller but it would radically reduce the quality.

LABOR COST:
1). Time in meetings
2). Time programming
3). Time testing
4). Time acceptance testing
5). Time working on case
6). Time wiring system in lab
7). Time wiring system at site
8). Time searching for parts and modules

LABOR COST: ROUGH HOUR ESTIMATES
1). 3 to 10 hrs at $__.__
2). 24 to 36 hrs at $__.__
3). 8 to 16 hrs at $__.__
4). 2 to 3 hrs at $__.__
5). 1 to 2 hrs at $__.__
6). 2 to 4 hrs at $__.__
7). 1 to 3 hrs at $__.__
8). 8 to 24 hrs at $__.__

This gives me an estimate of:
Low: 49 hrs
average: 73.5 hrs
High: 122.5 hrs

What I'd do is put all these figures into a spread sheet so that I could cook them a little until the nubmers looked the way I liked. You're taking the whole project and estimating the partil costs, average out the ranges, then averaging the totals to try to get a sensible expectation of effort required.

Time is the putty of projects. You can always expend more time to make a project work without it costing you real money. If a contract is important to get, you can reduce your time charges.

I think its important NOT to show all this information to your client. If you give him all this information, its an invitation for him to pick at it. The value of making such a list is that it makes you think about all efforts and therefore you're less likely to forget something costly.

There is an old heuristic that after totalling up your costs, use a standard multiplier for your industry to compute the final bid. This provides you with profit and buffer should things go wrong. A company I worked for once had a President that thought everything must be multiplied by 3.2 to determine pricing. In leau of thinking, I guess that worked for him. As an MBA, I think cost is less related to what I do to manufacture it than it is related to what the customer considers a fair or reasonable price. I'm please to say that the multiplier of some of my products exceed the 3.2 factor. Remember to that the factor I'm quoting is on a production line item. One-Time jobs are often done with higher or lower numbers depending upon the application and the amount of dollars. These factors are nothing but a way of adapting the price to what we think is right.

Babar mentioned a maintenace agreement - good idea. The equipment will break down from time to time due to circumstances and they'll need to contact you to fix it. Its best to quote a maintenance charge long before they need it. Often, it is done as a minimum visit charge, and hourly rate plus any replacement costs.

After doing this exercise, keep notes during the contract you're doing and see how your estimates compare with the actual expenses and time consumed in each area. This will help you better quote the next job with a profit.

Another note. People tend to quote at a ratio to real time. Some people quote half the time they should, others twice. Keep track of your estimates and actual times and overtime your either learn what adjustment ratio to use or you'll se your time estimates becoming more accurate.

When managing engineers, its common to keep a ratio in mind for each of your workers so that when they estimate a job, you can immediately adjust it in your head for a more reasonable estimate.

aka J