The $650.00 was the total of everything, not JUST Midas.

Taken directly from the TX.gov website:

Quick Facts:

Houston-Galveston-Brazoria Program Area: Brazoria, Fort Bend, Galveston, Harris, and Montgomery Counties
Dallas-Fort Worth Program Area: Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Rockwall, and Tarrant Counties
Austin Area: Travis and Williamson Counties
El Paso Area: El Paso County
Motorists must successfully pass both the emissions and safety portions of the inspection prior to receiving a vehicle inspection report, which will be used to obtain a vehicle registration sticker.
Gasoline vehicles model-year 2 through 24 years old are inspected annually beginning with the vehicle's second anniversary.
Remote sensing element randomly inspects vehicles emissions on highways.
All inspections are collected at a central database.
Recognized Emission Repair Facilities ensure quality repair of vehicles.
Waivers and time extensions are available for eligible vehicle owners.
To find the nearest certified inspection station, use the Texas Department of Public Safety(DPS) station locator Exit the TCEQ.
To locate a Recognized Emissions Repair Facility in your area, use the DPS repair facility locator

Talk to four different shops, you'll get four different answers. Same thing when asked at the DMV.