actually, the money doesn't go anywhere. it stays in the system. its just that, during the time that you invest. the price of btc is higher than the price of the btc that you are seeing the next day. it losses value but it doesn't mean the movement is always like that. if more investor will be interested on btc, the value of the btc will also rise. remember, the higher the demand, the higher the product value become. as long as you dont sell your btc when the market price is lower, you are not losing. moreover, if you sell it when the market is high, you will get a decent profit.