Random Sets in quest card shop?

I know that there is no longer a new set of random cards except after playing a match. However, I just noticed that for a particular card that is present in more than one set, the set IS random every time you go to the shop. What this means is that if you see a card you want but at a high price, exit and reenter the shop and see if it shows up in a lower cost set. Is this intended, or a bug?