Simply put, these items are everyday torches with Continual Flames cast upon them. They're a bit pricey, but it's also the last torch you'll ever buy. They don't emit heat, so you can't set pools of oil on fire - but they will work underwater, as they don't need air to burn. The light can be covered or hidden, but they can't be smothered or otherwise doused.
55gp on the average.