The lower-grade materia can still be valuable, depending on your server, and can be a nice bit of extra money for newer characters (who are likely to be getting their gear to 100% bond while questing). I've been selling grade 1 materia for 1000-3000 gil depending on the type. Grade 2 is less profitable, but occasionally sells, and grade 3 sells well IF you get a type required for relic or crafter quests.