We have one client who has had a Website Pipeline website for some time, after trying other options unsuccessfully prior to that. We were not directly involved in the implementation, but the client warned us (for future implementations) to define requirements in detail up front and write these into the agreement. They experienced the same with increasing costs, and felt that they should have stuck to the original quote.
The primary reason for selecting Website Pipeline is for the turnkey result. They do the website, the integration and the hosting, and this is great for companies that do not have anyone to seriously work on the website. The overall cost is probably not that out of line when considering what some pay for their websites. If the website is not a concern, then I would normally have the client look at IN-SYNCH, which has the most comprehensive integration in terms of the number of functions within Sage 100 that it integrates. They are also very good at integrations to Amazon.