That selling price is just above my wholesale purchase price so it could be ligitimate
However being that it is on Evilpay I would give them a 75% chance of being fakes
havig said thatRJ18Lm is th standard plug for B & S engines
B & S sold very few engines than past couple of years so they could just be surplus bought cheap.
However engine makers get their plugs in trays of 144 plugs , not in boxes so if surplus I would have expected them to be unboxed
FWIW the box and the act of boxing plus the 4 box carton accounts for around 1/3 the price of the spark plug .