Other thoughts:
Generally, I look for at least $100 off retail on a used lens (for the $500-$1100 range). If it's a hard to find lens, I might go down to $50-70 off retail. If it's an older lens, or an off-brand, I might look for up to $200-$250 off (example, an older Sigma lens).
For camera bodies, I generally look for a more aggressive discount. In m43: Take the OMD for example: While it was still $1,000 retail, they were selling privately selling for $700-800. Also, ANY equipment with a history of issues (OMD's bezel crack, X100 SAB, Canon 50mm 1.4 focus motor burn-out) get discounted used.
Supply/demand come into play. OMDs are for sale all over the place, driving the price down, EPL5 and EPM2s are a bit rarer, and already pretty low priced, so they are seeing less of a discount. I think Panasonic bodies come free with the purchase of a McDonald's Happy Meal. Not sure why, though...
One thing you might be able to get from FredMiranda, Amazon or whatever your local site is -- see HOW MANY are for sale. One or two? You might be able to price well. Sometimes you'll see just one or two other listings, and one is a ridiculous price. This is actually a great position for you! If you can be patient, price reasonably above the low-baller. Then someone buys the low price one, and the next person who just missed the low-priced listing figures they better get yours quick, before that one's gone too! (just make sure you are the SECOND-lowest price).
Two pages of listings of used items? You're in trouble, lol. Best option is to be the price leader.
The one thing you should NOT do, it price intentionally high. This just scares people away. Do some research on the price, take your best shot, and don't let yourself regret the sale.
If you have multiple items, give a discount for multiple item buyers. Remember, each additional item saves you like $10-25 on shipping, and you are tracking one less package.
The other thing I'd suggest -- if your item has major knocks and dings, come clean and price low. If it has really, really minor flaws, then list those, and let people know you are interested in "full disclosure" even though the item is mint except for this tiny rub mark near the battery door. Rate your item a 9 or something, and not "like mint" or "like new." I've found people are more comfortable when you do the nit-picky thing for them, and tend to trust you more. There is also less chance of them complaining afterward, and often you get feedback like "they listed a minor scratch, but I really don't see anything at all. Great Buyer!" Over-communication and conservative equipment ratings help your buyer, and in the end help you!