These are extremely cool atmospheric items but are rather impractical to buy and use in large numbers due to their relatively high price and have a limited duration. They are around 10 coins at the two merchants I've seen them compared to 3 or so coins for stinkweed fungus which is basically underdark tobacco. Seeing as candles can be made from rat/worm tallow, they should be relatively inexpensive. Tinderboxes can be assembled from dried zurkh scrap or what have you and would be even more inexpensive.
Alternatively maybe add candles/tinderboxes to being crafted through the cooking system and maybe add them as droppables on a few quests? Or even make them placeables like archery targets and barricades that can be selected and destroyed but last till reset.
I have to agree. Or allow multiple uses off one item
I would definitely enjoy multiple uses of these, given they have no mechanical purpose and just spice up areas for the odd ritual or whatever. They're a hassle to carry a lot of given their weight and expense, which seems a lot higher than you would expect from a ball of fluff or a dinky candle.