How much should I charge as a hobbyist?

With everybody's help here, I have neared completion of an inventory program
for my company. It uses a barcode scanner to remove parts from storage.
The user will have a way to print new barcodes for products that are not
labeled. It also has a couple reports (Crystal Reports) for printing
purchase orders, a complete inventory breakdown to submit to corporate, and
a usage report to see what has been used within a range of dates.

It also has an easy way of taking an inventory where all you would have to
do is scan the barcode and enter the quantity in the form so you could have
an accurate count (say quarterly or semi-annually).

The user can create a purchase order for whatever parts they need and when
the parts are delivered, the user can update the quantities received to
update the units on hand, etc.

I have created the database (Access) and will reside on a network drive.
2/3 computers will be in use as we have 2 parts rooms in the plant. The
Operations Chief wanted me to create this because our Corporate office will
not have anything for us for another 3-5 years. This is only for our
maintenance department where I work and the program and database was
customized specifically for this company. I didn't use SQL because our IT
administrator is an uncooperative bitch and won't do anything unless we
bring her Crispy Creme donuts. I tried to make this as easy as possible
since we have non-english speaking personnel that would use this also.

The maintenance personnel would only have to select there name from a combo
box, scan their part, and select the machine it will be used on. Oh.. and a
report would also show the cost of a select machine for a period of time the
user selects so we know how much we are spending on that machine.

What would something like this cost if one of you created this???

Tony K