It would have to go down further to be not worth doing, since he covered the cost in ten days, and the electricity cost is less than $2/week. At $7/week for example he would roughly break even over a year even factoring in the cost of the device.
You can make more money playing the ups / downs of btc (for example, right now, there is a down explicitly because gtx halted US dollar transfers so everyone is panic transferring BTC out and selling it off). Than trying to invest in a btc mining rig and playing a literal lottery with computing hashes, or joining a mining guild and making very little very consistently.
