Not really, no. There's a goblin you can trade 5 materia to, and he'll give you a random materia in return. Normally, you get materia of the same grade, but there's a small (~5% chance) that you'll wind up with the next tier up (for example, trading him 5 tier-3 materia will usually result in a random tier-3 materia, but with a small chance at a random tier-4 materia). It's not reliable enough to bother with in bulk. Your tier 1~4 DoW/M materia will always be nearly worthless.