I had two go through traditional braces and the combined cost was $11,000 for both of them. (They overlapped one year). We got a 5% discount for paying in full and also a small sibling discount. Our insurance picked up $2k each which was a nice surpise.
Around here (Boston) $5,000 - $6,000 was the average. Mine are both out of them know but still have retainers and go every 6 months for a check.
Some are higher but include more, others were lower but perhaps didn't cover all x-rays, impressions, etc.
Cost is only one factor so really be comfortable with your provider and the treatment plan.
Also, mine offered 3 different payment options. In full with a 5% discount, 12 months of no-interest equal monthly payments and finally an extended payment plan with interest.
The office staff did a great job of managing insurance info, etc. which I loved. I never was involved with any paperwork which was such a time saver.