One of our members @Lloyd_Plum also has his own mill in Plano and is a great resource. Great source for wood
Just to clarify so there aren’t any misconceptions, I’m a member of the forum, but not a member of DMS 
If you’re looking for cheap dimensioned lumber, I’m not really the guy. I mostly do live edge and custom log processing. I will occasionally have some cheap pieces, but I can’t compete on dimensioned lumber price with the big(ger) operations.
Ash is usually one of the cheapest hardwoods if you’re leaving a natural finish (poplar is often cheaper but is typically painted, though to each their own). I just got some from 4/4 from Dakota for <$3/bdft, but their prices do tend to fluctuate a lot.