I pulled a trigger on a cheap 'decoded' battery that clearly said that it works with my DSLR (D5100). It will take a while to arrive for China.
Others did that already and reported full compatibility with listed DSLRs. Look at reviews on Amazon.
Lithium-ion cells are cheap.
Nikon one is 7.7Wh....one can buy a premium power drill 54Wh battery for $100 at local hardware stores. If looking at Wh numbers alone the Nikon pack would sell there at $14 and that is the price the after market packs go for (shipped).