$280 for Huper Optic tint (ceramic) is completely reasonable. This is the best tint film for reduced cabin temps.
Suntech is a dyed film IIRC, and I'd stay away from it. Stick with undyed films from the major brands. Certain Llumar films are good, but not all. 3M is excellent quality, as is Johnston window films. Ask what each shop uses, and have them be very specific.
In my opinion, the tint film brand/type, installation process and overall quality of install should be your primary driver for selecting a tint shop, not price.