There are supposed to be four times more litecoins (84 million) than bitcoins (21 million) so with everything else being equal, Litecoin should cost 1/4 that of Bitcoin. But Litecoin is currently trading at about 10 dollars each while Bitcoin is trading at around 400-500 dollars each which makes it undervalued by a factor of 10.
Has it got something to do with the distribution curve (ie. more litecoins are produced in the first few years compared to Bitcoin)?

;DBecause the BTC is too expensive!!
Was just a joke, in fact, LTC is not cheap, just your illusion, think inverse relationship in the circulation and price