Sia Market Cap Value. Math.

Can someone assist in the math please:
I'm trying to work out a rough approximation of Sia's value. I know there are many factors that may make this number too far off the mark. However, I'm curious how to ascribe a value to the coins. The market cap of Sia should be the market demand for storage set in large part on the cost of storage at Sia (other factors like ease of use, security, etc not taken into account). Suppose 2$/Terabyte per month ( a number cited in the past) and 500 petabytes stored in the whole system (apprx Backblaze now). What would the market cap be given 53.5m coins?
Suppose:
53.5m coins.
2$ per Terabyte
500 Petabytes storedThanks.

Thinking more about it: The price of a Siacoin will be determined by demand. Demand will be a relation of capacity. Currently there is 300 TB of file contracts. But what is available capacity? If capacity is increasing faster than demand Sia price will be low.
I believe this will result in commodity like pricing whereby the low cost providers of storage (excess capacity and cheapest bandwidth) will sell at a price that it covers all the costs and offers a worthwhile return.
But how does that translate to the price of a Siacoin and hence the marketcap of the Sia?
How do we calculate a reasonable market cap range for Siacoin if we use a demand of 500 PB?
Thanks