Do you provide support services to users? If so, what is the cost or cost of additional add-ons? I've heard that this is priced a-la-carte per submitted request
civicrm has a community of professionals who provide commercial support. We - Fuzion - are one such company. Others are listed at https://civicrm.org/partners-contributors
The Core Team also do paid work, though I think they focus on bigger improvements - see https://civicrm.org/paid-issue-queue.
If you are a 'member' then there is a discount for the Core Team work - https://civicrm.org/become-a-member
Community provided support includes