I have been considering doing this and offering some of my web dev services as fixed cost, fixed scope productized services. $x for y service.<p>Have you tried doing this? What success/failures you have encountered along the way? What roadblocks have you encountered?
I have done it, it increased my business volume and when I stopped it decreased my business volume.<p>I stopped because I wanted to focus on recurring services and filled my schedule with these.<p>Most challenges with productified services come from risk management.
The more bespoke the work is, the more risk you have, and the more risk you have the more risk mitigation tactics you must apply.<p>I suggest that you read a lot on preventing scope screep and managing time estimates before diving in.
Jonathan Stark is a good start on that, he has free and paid materials available.
A roadblock you will encounter: common white label services are already freely/cheaply available. Blogs, guestbooks, all the Web 2.0 things. This will lead to "why should I pay you when X does it for free". You'll need to find a way to differentiate and add value. Most of the players in this space have consolidated and now are operating at scale. Honestly, you should have jumped into this 15 years ago.<p>If you're referring to custom development but with a fixed scope, good luck with that. That's the whole job of a PM - you may want to get some help with that if you don't have experience in doing it.