In my experience, properly printed, trimmed, collated, and put together stuff looks a lot better than DIY even with modern colour lasers. Of course, depends on what you doing and how professional you need it to appear.
About £300-350 sounds about right for a full service digital files to booklets.
Goes without saying proof it and proof it again. Mistakes have a habit of making themselves very prominent when you have a hundred copies sitting in front of you. Even more so when there's 30,000 of them. Don't ask.