Ouch, that's quite an increase :( I wonder if there are more accurate wholesaler utilities/dealer utilities that have better counts of units for sale that way. I'll have to ask my buddy.
Living in Austin, TX, I get my windshield tinted as well. It gets so hot here. No way am I going without tint on all the glass. The summers are brutal and the vehicles cook inside already. I need all the help I can get!