It depends on a lot of factors:

1. What are the requirements/scope for this Help Desk system?

2. What is the scale of the system? As in, how many users are you expecting to use it?

3. What programming language, web server implementation, operating system are you going to use.

4. What features are required for the system? E.g. Load balanced / failover capabilities

5. How customisable the system will be?

6. Does your cost include hardware, network infrastructure? Think about licensing issues too.

Back when I was a college student, I did a free lance mini payroll management system. Using Microsoft Access as the database and Visual Basic 6 as the front end (thin clients were not too affordable and popular yet back then), the system had to support only 5 users. There was no need for transaction control, and ODBC was fairly sufficient to do the trick.

The system consist of data entry forms, search and query functions, automated calculation and tabulation and reports.

All hardware and software licensing cost was footed by my client.

I billed my client around RM4,000, just for the custom solution. Well, that was like 5 years ago.