If a coin has a low total supply, it means that the maximum amount of coins available are very little in number. You can use the coinmarketcap website to see which coins have the most or the least value. So if you click on the circulating supply tab after you open the coinmarketcap website, it will list all the coins from the highest total supply to the least. If the arrow is pointing up, it lists the coins with the least total supply, if the arrow is pointing down, it shows the coins with the most supply.
As you may realise, most of these coins are quite expensive. Even though they don't have a very high marketcap, the small supply makes the coins more valuable so more expensive.
Bitcoin has 21 million coins in circulation. Let's have a look at zcash, it has around 3 million coins in circulation. That's around 7 times less than bitcoin's. The supply is really limited and this drives the price up, as you see, the current price of this coin is just over £250 each (currently). If it had the same amount of investors as bitcoin currently has, the price of this coin would have been around 7 times higher than bitcoin's so it would be around £71,516 each coin if it had the same marketcap as bitcoin.
Bitcoin is more expensive than this coin because bitcoin has a bigger market cap so basically, more people have invested in bitcoin.
Market cap means the total amount of money invested into the coin. Marketcap drivided by the circulating supply is what determines the price of the coin. So let's do the math.
if you divide the circulating supply of the coin by the market cap, you get the actual price of the coin.
You don't divide the coin with the total supply because the total supply means the maximum amount of coins that will be available, after everything has been mined. Currently, a lot of bitcoins haven't been mined, so they're not in circulation yet. However, after all the coins have been mined, you can divide it by that number. That just tells you the maximum amount of coins you would have after all the coins have been mined. For coins that do not use mining, the total supply and circulating supply will be the same.
For example, withIOTA, the the circulating supply and the max supply is the same because you don't mine this coin.