I did not read the entire thread but I run the office of a builder/real estate developer and we do a lot of basement suites (while we are building homes), we are usually in the mid range of your quotes. As far as the size of business we are; we build about 10 - 15 homes a year. Our staff is about 10 people and no one on our staff drives Hummers
One thing to remember though, is that a contractor that is fully insured (liablility & WCB), has staff on payroll (not subcontractors), and is up to date with a warranty company will have a higher overhead and will need to charge more to have any kind of profit margin. I think that most developers are looking to make about 10 - 15% profit, but also add a 10% contingency to esitmates as well, in case anything goes wrong.
Lately we have been working with homeowners on a cost plus basis and are saving them money (usually at least the 10% contingency). This might be something for you to look into, just make sure that if you go that route, you agree upon the wages you will be paying the developer and his staff (ask for the developer to supply their timesheets when they invoice you), and that they supply you with copies of all invoices pertaining to the basement suite. Full disclosure is really important in a cost plus contract to make sure bills are not being padded before being passed on to you.
If you cannot legally install a kitchen in your suite, and your contractor does, it most likely will not be covered by your contractor's warranty company and you would be dependent on your contractor's good will if anything goes wrong down the road.
HTH R