The common Flu also infects a good billion people each year, much, much more than any other disease. And how many percent does it kills from that billion?
Also, keep in mind the first detected cases of the disease are not even a month old. As a result, both the death toll and the confirmed cases of infection are rising fast. Right now already, there are 106 dead, 25 more than yesterday, all while the confirmed cases almost doubled to 4652 in just one day.
Plus, there may very well have been more cases, but misdiagnosed as a heavy pneumonia instead (just like what the new coronavirus was originally considered to be). In other words, those 106 are the minimum and the real death toll might be quite a bit higher than "only" 106.
To be fair, on the opposite end there are probably thousands more who have been infected but displayed only mild symptoms and are flying under the radar. Whether their viral load was high enough to transmit to others - same with those in the incubation stage - remains to seen.
You're right, though, that if this new Coronavirus infected 1 billion people like the common flu, we'd probably be seeing 20 - 50 million people dead at the end of the year. That's almost World War or Spanish Flu levels of bad. China is totally justified in their containment procedures so far, in my opinion.