Don't drop your seat prices now, it's too late for this season. If you promote (which looks likely) you'll want to increase some of your seat prices. Your bleachers might be the exception since they're only half full. You probably shouldn't have had them higher than $12 this season. $13 next year might be right.
But don't take our advice on this, the best way to judge if your seat prices are good for D3 is to look at several D3 teams and see their prices/capacity.