Now it did not take too long, but HEX already has third party site that sells individual cards, of course digital as the game itself is digital only.
Knowing how popular it is, this was simply matter of time, but even before the official trade function being in place i.e. currently everything you order will not be delivered until the official application start support trading. Since the upcoming patch’s auction house function does not include free trade function yet, I am not sure even that functionality is enough to get these purchases delivered.
However, the important part is that this proves the strong community support of the game.
It is hard not compare against the golden standard here, which is Magic the Gathering Online. They have also third party vendor selling individual cards. Magic economy is very well established so if you compare major third party vendors, you will see the prices of individual cards are relatively the same. If there is significant difference, that is because one site is ahead of others, and eventually the others follow.
Even though Magic Online has player to player trading system, not a true auction house system, their posting are generally same price as the online stores. Why? This is because the posters are basing their prices on the others, and some of them are basing on the online stores.
The difference here; however, for HEX is that there is nothing established yet and the prices set by HEXTCG Pro are just by their own speculation of how much the cards can potentially worth. Though the relative price differences may be correct, the actual price may be far from what they are setting.
As of today (5/31/2014),
Two cards above are set for the highest price in the store for $14.00 each.
Since noone knows (unless you have insider information) when exactly the trading function is coming, it is wise to avoid purchasing anything from any third vendor for now. The auction house system is significantly different from the Magic Online market where third party vendors, or someone.. has a way to set a standard price on the market.
With a true auction house, which HEX will have soon, players/community will declare the value and we can see how much each cards were sold, and quickly find out what each cards are worth. Basically, this a Ebay not Magic Online third party store market!