Maybe Trading Lore would work?
I think the usual description is "you know where to sell the goods for a profit and where to buy cheap". It wouldn't be much of a stretch to include "you know the value the goods".
I think Trading Lore is about the theoretical part, not the actual part. That'd make you a good economist, but not a good trader.
As I see it a person that train horses will know (at least a little) about the prices or how much os worth his work.
Only if he's also in charge of the logistical part, which is often not the case. For instance, the horse groom of an inn doesn't have
ever to buy a horse. How would he know the cost? It's like asking a computer engineer to know the cost of his computer parts, something he wouldn't because he's just not the one buying them. Or an building worker knowing the price of what he builds, something he wouldn't because he's just not the one selling them, nor the one buying the materials.
An adventurer fighter (game semplification aside) will know prices and overall availability of the tools of his trade.
Only if he buys it himself, which is totally independent from his actual expertise in swordsmanship. For instance, you'd expect a knight of noble birth not to have any idea of his sword's price, because chances are that he doesn't buy any himself, but merely asks his people to take care of the payment after he had chosen a sword he likes.
I don't expect a thief not knowing how much a lockpick set will cost or how good it is.
Once again, only if he buys his himself. If he's a member of a guild and the guild provides him his tools, why would he know the prices?
Trading is to barter on prices (at least as I will use it), but to appraise quality (especially for specific tools) a roll on the "using" skill is more appropriate.
Ah, but to efficiently barter on prices, you need to be able to appraise quality.