Tue Feb 12 2019
An awful lot. That's the short, short answer.
I have not done enough research on this subject to actually back up this claim, but I think that so many of these things come and go on a daily basis, that there is no solid, factual answer. It's ever changing.
The really amusing part of this is the difference in value at which these coins exist. They range from the top value, Bitcoin at about $3600 USD at the time of my writing to something like Stronghands (SHND) at about 0.00003452 DOGE. Which itself is worth $0.0018 USD. In other words, the Stronghands coin is worth WAY less than a penny. So low that I couldn't even find a direct USD conversion and had to use DOGE as an intermediate.
This is also the reason that so many exchanges exist. There will be another article about that. For now just know that not all coins are available on all exchanges. Which may or may not be a problem depending on what your are intending to trade. In the early days of my experience I found myself mining a coin, and found out that it was only available on a handful of exchanges. I found one. Which is great! But it was not an easy process.
Facebook Decides to Make Their Own Cryptocurrency
Satoshi Nakamoto's Identity Revealed
BTC Breaks $7000 this week