Linseed oil turns black as it ages, giving a lot of old rifles a very dark look. They can usually be lightened up a bit using Scott's Liquid Gold or Johnson's Paste Wax to remove the ground in crud and 100 year old oil.
The reason the 1886 Lebel rifle costs so much is rarity. Lots of them were captured when France surrendered to the Germans in 1940. After WW1, many were sent to backwater troops standing watch over France's former colonies (Morocco, Algeria, Tunisia, etc). Most were old and tired and mothballed when the Germans captured them and many were in severe duty situations for another few years after theat. So, price is not necessarily an indicator of good design nor of desirability, but in many cases simply rarity. I have an old 1895/05 Berthier (served with the French army concurrently with the Lebel rifle), and I wouldn't give you a penny for the thing in a combat situation (except maybe as a club, it is heavy).
One bit of trivia- the Lebel rifle and its 8mm Lebel cartridge were the first rifle/cartridge designed for smokeless powder. Other than that, the rifle is not known for anything interesting other than being one of the most common rifles dug up in French farm fields over the past 100 years.