$0 - Nothing! Support is part and parcel of the subscription. You need not pay any additional bucks for support.
You can look at the Pricing page to see the different levels of support that are provided for the various plans. Feel free to send us an email at email@example.com for any issues that can’t be resolved from the docs. We’re always happy to support!
There is a premium support that we offer for a fee to our enterprise customers. If you would like to get more details, send us an email at firstname.lastname@example.org