I don' t know how $5 worth of string can cost $35 to $100 bucks.
The string may be only $5 worth of material, but a company has to pay a guy wages for 30-45 minutes, to make the string; Has to pay rent, insurance, utilities, etc, on a building to make them in; pay an office staff, purchase ads, and hundreds of other expenses in running a business. Then, the company may warranty their work, deal with customers questions and with all this, they still have to make a profit to stay in business. Combine this with the fact that there are many, many places to get a string and you can see why it' s pretty difficult to charge more than the string' s worth.
Now, if you want to do all the above, expect to invest a few hundred dollars into a string jig, string material, serving material, serving jigs, etc. It will probably also take an amateur about 90 minutes to make a string. If all that is worth saving approx. $35 on a string, then the following link will get you started.

By the way, I think it' s worth it, that' s why I make my own. My preference happens to be Brownell' s Ultra Cam material.
[link]http://applearchery.com/building_bowstrings.htm[/link]