The Everburning Torch costs less than 110 gp because the price is brought down by the fact that sometimes wizards cast lesser planar binding and conjure Lantern Archons, and get them to work for a few hours making one Ever Burning Torch per round. This works out to 600 'Torches per hour - at the cost of a single fifth level spell.
A 5th level spell costs 450 gp to get cast, so assuming that that the Lantern Archon is himself paid 26,550 gp for an hour's work we can easily see that the total cost for creating all 600 torches is 27,000 gp - from which we get their combined market price of 54,000 gp. Spread out amongst those 600 torches the average market price per torch is therefore 90 gp - which is precisely the listed value.
-Frank