Yes, most coach companies invoice the company directly on the basis of its KVK number (the Dutch Chamber of Commerce registration).
For groups from about 10 people, a shared coach is almost always cheaper, and it also spares you the hassle of parking in the city.
No, it is a price estimate based on your route and group size, not a confirmation of availability. The coach company itself confirms the final price and availability after you have sent a no-obligation booking request.
No, requesting a booking is always free and without obligation. You are not committed to anything until the coach company has confirmed the final price and availability and you agree.
Amsterdam and 40 people are ready. Fill in your destination and your day.