If you and your management aren't behind the project from the start, don't do it. The best consultant in the world won't help. Yes, you have every right to know what consultants are getting paid, no matter what the sales or business-development people say. Ask what solution the consultants are proposing. If they are, you don't need consultants.
Maintenance is arguably the most expensive part of any business system's life cycle.
Therefore, it's important to be able to efficiently maintain whatever system you get from your consultants. This can be accomplished partly in the form of documentation and should come with what you're paying for. If you retain the rights to the system, know how it works. It's your software, so if you don't know how it works, your consultants will be back many times after you're gone. If your consultants aren't willing or able to do this, don't hire them.