So I've been running the RotRL AP for a few months now and my players are finally done Burnt Offerings. Personally, I'm new to GMing (though I have a lot of experience in role playing and tabletop) and several of my players are new to the system/format, so I've been introducing rules and concepts slowly so as not to overwhelm. My next system to implement is going to be the appraisal/treasure stuff. So far, I've just been telling players as they get treasure, "X item is worth Y" and they sell it and go on their merry ways, except for adventuring gear which sells at 50% (per rules).
The AP basically outlines treasure in two ways -- either it's adventuring gear the PCs can take and sell for half value (or use), or it's treasure with a given gold value as outlined in the AP (usually a "Treasure:" section for the encounter). And then, of course, there's just piles of gold.
How does appraise tie into this? How have you run this or might you suggest I run this? Do they need to appraise the value of the treasure in order to determine if it's valuable or not? Even if they appraise poorly, the shops are only going to give them what the item is worth in gp, so it's not like accurate appraisal is really going to change anything, especially when my PCs have a tendency to loot anything that could be remotely valuable as long as it isn't nailed down.
I just make appraise checks up as appropiate. For instance: the description says that amongst the tools scatterede around an abandoned smithy are some masterwork tools (or weapons). I have my players roll appraise versus som DC I make up (usually 10 or 15), and only if they succeed do I tell them it's masterwork. Unless they're extremely poor, they're not likely to loot a standard non-magical dagger, so if they fail the check, and thus fail to realize its worth, they'll just leave the masterwork weapon behind.
For non-standard treasure I do the same; make up a DC and have the PCs roll appraise. Even if they know these old gold are worth something to collectors, they'll not realize the full worth with a failed appraise check. And thus, they could sell the 2500 gp collectors ietms for 2000 gp (I assume any merchant is attempting to cheat the poor, clueless adventurer who obviously doesn't know what the stuff is worth).
Piles of gold are not appraised. They just count it, and that's it.
Yeah the idea behind Appraise is to a) let the party know if something is actually valuable ("this statue is carved from marble and is worth 500 gp" as opposed to "its carved from a common rock and only worth 5 gp) and b) let the party know just how valuable it is. So a statue may be worth 500 gp, but a poor appraise check might make the PC think its only worth 250 gp. Thus, when the merchant offers 175 gp for it, while explaining he still needs to make a profit on resale, the PC thinks its a decent deal when in reality he's getting stiffed.
As mentioned above, it depends in part on how much you want to roleplay transactions with merchants. Do note though that even if you do not want to roleplay the transactions, you can still apply appraisal checks. Simply tell them the item is worth X% of its actual value based upon the appraisal check and then let them sell it for that amount (or fraction thereof depending on campaign).
The main thing to consider is how much do you want your players to consider the entirety of their character sheet. The main reason to call for appraisal checks is to let the players realize that there's more to the game than simply killing stuff. It might encourage a player to apply some of their skill points to appraisal if they are being asked to appraise on a semi-regular basis. It helps create more rounded characters and draws away from the min-maxers out there.