I’m trying to get around your thought process here- but the kill buyers have a contract to fill a truck. They WILL fill that truck if you are there or not- not unless you can afford to buy every horse that goes through. So if you can stalk one KB and bid against him so he drops out of the bidding on a specific horse- he’s going to buy another horse to take it’s place. So while you have saved the life of that specific horse- you won’t have changed the number of horses who are going to get on his truck. It’s not like you are buying the spot on his trailer.
So the way I see it- EVERY horse who has a home is a rescued horse. Buying the most pathetic unmarketable most likely to be killed horse may just put a more fit marketable animal on the truck in his place and put a greater burden on you to rehome an animal no one wants (if adoption or resale is your aim) I don’t know if that’s the right thing to do with your resources… but the art of rescue business choices seems to be just as tricky as the KB art of grading a horse by sight.
If you skim the cream off the auction house herd- and select the most marketable animals- perhaps you can turn them over quickly- and have a high volume of “saves” … if you scrape the bottom of the barrel- maybe you will spend thousands to rehab a horse no one even wants.
You have to philosophically figure out what does “money best spent” even mean? There isn’t a clear best answer.
I suspect some rescues prefer more desperate pathetic horses because they bring in donation money and have dramatic stories. The proximity of the horse to the kill truck seems to be how “rescued” the horse was.
Also- lots of killer buyers will buy up good horses and try to remarket them before shipping over the border. They know where there is money to be made- so if auction crowd is weak- but the horse is good- they may snap up some good deals for resale too. Don’t assume that they intend to ship everything they buy.