Rim Guard seems to me to be cost effective from what I have checked on. I had called a dealer last week and they said it would take about 110 gallons for a pair of17.5L-24R4 tires. Total cost would be $330. It would give me about 1200# (11# per gallon) total ballast. That is about .27 a pound. I know it is not readily availible everywhere.
I know I dislike calcium for sure. You have to have a tube. It eats rims and nothing worse than getting a cut tire in the field and having a dead spot. Also it seems when you cut a tire before you can get the cut on top it sprays the tractor.
Around these parts it is either iron weights or calcium. Rim Guard is catching on though.
I have been around farm tractors all of my life had not heard of using anti freeze or window washing fluid. I thought it was an intersting idea though, but does have some draw backs as well.
Window washing fluid at $1.20 a gallon and weighing around 8# a gallon will come in at roughly .15 a lb. You may have to buy a pump and a valve for your value stem. I haven't priced either one of those items.
50/50 mixed antifreeze would be around .37 a pound. Now if you save your drained anti freeze or buy a used barrel of antifreeze from a car salvage yard you can get that down pretty cheap.
Rim Guard is very competitive when you compare it by weight rather than by gallon and if availible in your area the dealer fills it for you.