My cab has rolling door latches that allow the doors to be locked but open about 3" for air circulation, has a "moon roof" that can be opened for ventilation, rear window opens fully if you want the open air experience. With all these open, it is good for spring time operation if the work isn't dusty or buggy, but come summer, all the doors get closed up and AC turned on. No limbs beating you in the face either and it cuts down the pollen I breath in when mowing which helps my allergies a lot.
When you think about the cost ($4500) divided by 60 months that equates to about $75 per month or $2.50 per day which is less than a cup of Starbucks coffee. Not a lot of money spent to allow working in comfort compared to being hot or freezing, attacked by wasps/bees/horseflies etc, breathing in dust and pollen, covered in grass debris when baling hay etc. To each his own as to whether the cost of a cab is worth it or not, but I dare say that most folks who think the cost it too great piss off more money daily on coffee and beer than what a cab cost.