Possibly $0?
I just saw this great post linked from @chrishajer about doing the encoding as a part of the webhook that describes most of what you are trying to do. In a separate forum post related to webhooks I also shared a few ways that Gravity Flow’s outgoing webhook gives you a little more flexibility to write no/low code for such an effort. Hopefully those links might give you, or the developer you find to assist you, an easier time in building what you need.
Cheers,
Jamie