Terra Pass is getting $10.91 ton for their carbon, and there getting
it because it is so simple, professional and easy for people to
understand and more importantly, trust.
A 3kW PV & 40gpd solar thermal, that's 8-tons a year of offset credits or (8tons/yr x 25years x $11/ton) $2200 to the exchange and $1760 to the system purchaser, on the front end.

For a $25K system we sell in New Orleans, with $17.5K of Federal & State incentives, that leaves $7.5K of unmet cost, making the carbon ~ 25% of the total out of pocket expense. 

Of course we might be able to tell a better story here in New Orleans and get $25-30 for our carbon, which would make the carbon worth over 50% of the up-front costs.  Regardless of who supplies the solar, its $440 for the least of systems, but on a 3 system family its over $1K for managing electronic paperwork.