Gear is bought to be used, so the price follows usability more closely than looks.
The two questions that set the number
Does it work? Demonstrated, untested, or known faulty. Is it complete? Every piece, missing pieces named, or sold as parts.
Answer both in the title and the right bidders find you.
Where to start
Everyday gear: low start, quick pace, lots for accessories. Good room-builders, and this category rewards volume.
Premium or current-model gear: start sensibly and use a reserve. A quiet night is not the night to lose a good tent.
Age is doing a lot of work
Coatings, elastic and foam age whether or not the item has been used. A ten-year-old unused tent is not a new tent, and saying so plainly makes the rest of your listing believable.
Delivery is part of the price
Bulky items cost real money to post and a buyer who has not thought about it bids as though they do not. Say the position in the listing, and offer collection on the biggest items.
Lots
Pegs, cords, mess kits, small spares and accessories sell well bundled. Keep anything premium out.
Questions people ask
Should I price against a sale price?
Know the current price, then price the gap honestly on age and condition.
Do repairs lower the value?
A declared repair barely does. A found one costs the sale.
Is it worth selling incomplete gear?
Yes, as parts, clearly labelled. There is a real market for a spare pole set.