I was taught something a LONG time ago that seems to get more true the longer I have horses.
Sometimes in order to 'win' in horses you have to 'lose' first. Lose the feed bill, lose the vet bill, lose the farrier bill, lose the board bill (for those that board). In some situations the only way to 'make' money is to lose some first, then you can make it up in what you save.
Not real cheery advice but everytime I pretty much give away a horse for a lot less than I wanted, I remind myself that feed for one horse is about $2000/year, the farrier is $300, the vet around $250 if I have no accidents, if the horse is at a trainer's barn then that's about $9600/year with no showing......and on and on and on. I generally feel better after I'm done running the numbers in my head.