There are a two Miniature Equine rescues in NorCal - AngelsForMinis.com and GallopingAngelsRescueandSanctuary. I refer people to these two that want a pet and don't want to pay what my pets go for! Also if someone wants a Mini, I always encourage getting two, so send them to those ladies for a companion to their Mini.
As for buying from a kill auction. If you're not buying from a kill buyer but bidding at auction, you're likely saving that Minis life. Buying from a kill buyer - they're just making $$ off people, as they still fill their quota regardless. They just cherry-pick the most saleable ones and offer them up in an "buy now or it's on the truck" type marketing.
One thing I keep telling people - contact your local rescues (any equine ones or local vets) to have gelding clinics for low cost geldings - and encourage them to let breeders take advantage of this and get those boys gelded! That's one of the reasons many breeders don't geld is the cost, especially in areas where they don't get much for their colts. I have one that's a normal gelding and it's close to $300, another has retained both testicles and it's between $1,000-1,400 (he has to wait until this fall so I can save for that). It would be I imagine, hard to justify, if you have to spend $300 and sell for $500, you're way in the hole on that and definitely hard to swallow.
But rescues view breeders as the enemy and shouldn't - responsible breeders are for the betterment of the breed. Work together cooperatively to geld excess colts. Educate people on what a decent conformation/good attitude/etc., Mini is. Even a pet or no-papers Mini can be a good example of a Mini. Most never step foot in a show ring, but breeding for pet quality is a lose=lose situation. Breed for high quality and be glad they get a lifetime pet home! Sadly spaying mares is still prohibitively expensive, but one colt can have sire more foals in a year than a mare can ever have. Breed responsibly and rescues not having that God Complex would solve lots of issues.
Okay my .02 and off my soapbox!
** Please no rants about breeders causing all the problems. If you have one foal a year (for yourself) or think you're a "small" breeder or are breeding unregistered pets - you are just as responsible as someone breeding 10, 20, 30 foals a year that may have a great market for their horses. Besides you have no control what happens when that horse leaves your hands. Life happens and you can't know for a fact you'll be alive/capable to care for horses you bring into this world. Not going to defend those that dump their horses at auction - big or small - I find that repulsive.
Really off the soapbox this time!