It usually is a quantity thing. If you hold up and wait til you have 100 ounces of PGMs, or equivalent amount of values in the resin, then usually those fellows are really nice to you and will give you much more money. Also you can be a little demanding when you have a quantity like that saying things like "well, if you want another 100 t. oz. next month, then I think I'd like a fairer price, or maybe you can waive the assay fee?"
There are many ways to skin a cat
I've mentioned before that I'm working on a dry process that involves heat and a halogen gas. Then there's an aqueous work up (pretty much dissolve the salt, oxidize it, then selectively precipitate it).
Conventionally it's: dissolve substrate, then dissolve residues (Pd and Pt, fusion for Rh, or direct halogenation).
I've also heard of people using ammonium bromide, sulfuric acid, and oxygen/H2O2 in an autoclave at couple hundred degrees or so, 96-98% yields IIRC. This is from what I remember of a patent from the South Dakota School of Mines... I can dig it up if anyone wants it?
Also heard of 170C cyanide leach which boasts 98% yields. Again, from a patent, I can go find it if anyone wants it.
Louis