>It makes sense to have a service contract when you have really no knowledge at all on the domain, but as soon as it's related to your daily job then you will quickly realise that experts are mythical characters whom your contractor have no better access to than any other company, including your own.

I would seriously question who you're doing business with. Anytime I have had a significant issue, the escalation path is to the guy who wrote the code. To imply that enterprise support is just a bunch of people who don't know more than the average guy off the street is ridiculous. Tier 1 support? Sure, but you don't stay there long if you're a clued user with a real issue.