i read an quite interesting, but obviously hidden commercial, posting about build or buy a solution for EDI. it’s right, that this is often not an easy decision, if you need a new module.
one point is missing in that posting: if you buy a so called ready-to-use solution, in most cases, it is not ready-to-use. you should reckon at least 30% of the budget for customization. The custom solution can be the cheaper solution, if there is no buy-solution on the market or the available solutions are only usable with a huge amount of customizations. For managing a custom project you could read this blog posting.