Why people don't just answer the question is beyond me. I mean, why post if you can't contribute to the answer?
"Very roughly", new construction runs $70-$80 per square foot. "Oh-niners" in Terrell Hills have some expensive finishes to make the property compete with that upscale neighborhood. You could go well into the $125 per square foot range or higher depending on how nice you want it.
See, easy answer.
Keep in mind that ALL new construction builders are hurting for business right now, and have been for over a year. If you decide to do new construction, get your plans and contact several experienced GC's to get bids and negotiate everything, especially the finishes. They have the biggest margins on labor, paint, and flooring. Or you could save A LOT of money if you're up to being the GC yourself. Contact UBuildIt (if they're still around) for info on that.