Genesys is the SMS broker (at least indirectly) for SMS in Genesys Cloud. They will charge you around $2.00 to obtain a long code number and $3750 or so for a short code. Then there is either a $1.00/month for long code and something like $3750/quarter for short code. Check out the resource center for pricing and regionalized support.
Also, every text in or out will incure costs listed in the resource center as you have found.
Yes, you can purchase 800, mobile, or DID SMS numbers and you can SMS-enable GCV numbers:

Using an 3rd-party SMS vendor is coming. I think Twilio is one of the first they will bring out.
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Robert Wakefield-Carl
Avtex Solutions, LLC
Contact Center Innovation Architect
robertwc@avtex.comhttps://www.Avtex.comhttps://RobertWC.Blogspot.com------------------------------