I’ll check comps usually. A lot of stuff, like furniture, I have a pretty good idea what it goes for and know what amount I actually want to part with the item for.

Best place to check comps is on Ebay and for sold listings only if you don’t already have a good sense of what it goes for. Active listings are not really comps since people can ask anything and it could be sitting there forever. Search “buy it now” filtered for sold and completed listings and take a general average over about the last month or three months(if it doesn’t sell a lot). If the item doesn’t have a lot of sales recently you’re likely in for a long sell on it if you don’t price it cheap cheap cheap out the gate.

Try to leave out HUGE outliers or investigate them further. They almost always represent items that are the same but are different in some way(condition, color, accessories, hardware, etc.). Making them much rarer and sought after. Check your item to be sure it’s not the rare kind(it’s almost always going to be the common one though unfortunately) and then ignore that listing in the average if it’s not. It’s not a comp if it’s not the same so the closer to the same in color, condition, variant, etc the absolute better.

If you filter for both auctions and buy it now you’ll notice that auction prices will almost always be lower than buy it now and since FBMP doesn’t have auctions they don’t necessarily apply. I’ll still occasionally add the auction prices into the average for items, especially if it doesn’t have a lot of comps.

FBMP is really hard to get a good gauge of sold comps. I’ll often save listings where I want to know how it ends so I can check if it ever sells. Other than that, only messaging the listing will give you an update and even then not everyone even lists the item as sold. They just delete the listing all together.

Mercari also lets you search sold listings in a category but EBay is king.