I was curious about this question so I searched and found this thread - my idea is similar but with a twist. Rather than pay GasBuddy to get their data, why not a data sharing agreement? GasBuddy data flow to Waze and Waze price updates flow to GasBuddy for their users? There should be no reason a business solution couldn't be made that works out best for everyone.
Alternative, maybe Waze could sync to GasBuddy data for updates the way it does with Foursquare? You sign in to GasBuddy with the Waze app and it posts the data for ya?
There seems to much potential for a good relationship between these two services!