And finally this table, which I think will probably do it for me today. I'm on a holiday, which is comfortable, but I wanted to get something out for the gentle reader.
To be honest, the above table abuses the term 'farrier' somewhat, as the profession applies traditionally just to the care and shoeing of horses hooves, and not with the whole horse. But for simplicity's sake, and to keep my player's sanity whole, I have decided to include articles of general tack as well.
Note that a hippogriff's back feet require shoeing, but not the front. The front are claws, and the player can choose to increase the amount of damage the hippogriff does by adding iron talons ... the difficulty is that the talons are uncomfortable for the hippogriff, which takes time to adjust to them and tends to be 'surly' in the meantime.
The cost of most things on this list is quite cheap, and things are usually available. It is only by chance that the salt lick or the bit for horse isn't ... most of the time, they would be. But the fact is that sometimes a town sells out of something, or everything is claimed by someone else. This of course doesn't keep players from stealing something they really need, if I can determine that it's likely something is around that is owned by someone. That involves going into the guts of the table and making a DM's call on the matter. As it happens, the problem hasn't come up. The party knows that in a week the item is likely to 'come in' and be available for purchase.
Well, that about covers it.