1. We use a proprietary cms.
This is a whole different post, but in one phrase two heads are better than one. We have yet to see a proprietary cms that can beat out Joomla or WordPress in terms of usability, functionality, reliability, or security. I don’t care how many other companies fell for their gimmick.
2. We’re social media experts
An expert wont tell you, Google will.
3 We’re good at traditional and internet marketing
Really, or is it that traditional media is dying and you guys switched to survive. Don’t pay a premium for a novice. Check their track record and ask for real world examples.
4. They have more than 20 employees.
Is the top leadership focused on your project or the bottom line to cover all their overhead, the same activities will produce different outcomes when the motivational influence is different. Good coders can bang out projects fairly quickly if they are experienced and have a solid code library to draw from. The larger the company, the more disconnected their corporate culture becomes. Which is why large web companies are the last to adopt new web technologies.