if you own the item, you can see both how much it is sell-to-site-wise and trade-broker-wise (sell-to-site price is in the lower left of the info popup, and Trade broker sale records can be seen by selecting and clicking the 'broker item' button)

However, since all equips of the same level share the name, and you haven't listed the rarities of these ones (and there aren't that many lv10/15 equips in the trade broker), I can't really guess (the lowest level equipment I own is Tattered/ lv20 gear)
Uncommon ones are probably worth 100-200 gold
Rare maybe 200-300 gold
Epic might? be 500-1000?
Legendary 1000+? (only available from fest zone bosses if you have a team of the right level I think? So it could be worth a lot more on the broker)
(there are no mythicals for any levels other than 25 and 50 so that's a moot point)