You can not tell. But no. It's three days ago a meticulous calculation published on Reddit by the user Seaserpento2, entitled "How Much Does It Cost To Travel To A Gore?". On the post in question the user explains that he has created a program on Python which simulates the opening of packs, transforms duplicates into dust, collects cards and stops the count of packs once a certain amount of cards and a sufficient amount of dust have been collected to craft the rest. We remind you that Hearthstone: Journey to Una Goro introduces 135 new cards, including 49 common, 36 rare, 27 epic and 23 legendary.
After several attempts, according to its calculation, the amount of minimum packets to complete the collection would be 214, while the maximum amount 437. Taking it as a standard the average of 316 packages and referring to Blizzard prices ($ 49.99 for a bundle of 40 packages, 8 would be needed) the calculation is fast and exaggeratedly high: about $ 399.92. This is where you say "good".
To leave no doubt Seaserpento2 has made available the source code, in case you want to do yourself a try.
In any case, whatever the price you were to come out of, the warning I feel about doing is this: DO NOT spend to win. On the other hand, in a game like this, you can have all the existing cards and continue to have no skills to use them.