The system that we build together is your system. It is important that you understand what it does and how. You could hire a consultant who builds you a black box; but if---make that when---anything goes wrong in the future or your needs change you will have no recourse other than to call them back and hire them again to fix or enhance it.
I don't want to build black boxes. (Not that I couldn't or wouldn't if that's really what you want, of course...)
Instead, I work with you to teach you about the (very possibly new to you) technologies necessary to build your system. All the work I do, the technologies employed (and rejected) and the system internals are documented openly. This information is accessible to you at all times, usually on your own intranet. Questions are encouraged and tutoring is an essential part of the service.
I feel that openness and ongoing technology transfer is better for you and better for me. You'll know what you're getting and I'll know you're getting what you need. Maybe you'll choose to maintain the system we build together by yourself and not hire me for further work on that project. That's OK. But I expect that you will consider me again in the future for a new project because you know I can and will help you learn about the construction of your system and the technology it employs.