Wow, folks! We are getting into an area where only one's own personal opinions can speak.
Grapes are not designated DOCG, wines are, and only prior to bottling after they have been analyzed and tasted by Italian Government licensed personnel.
You can't put even the best of grapes from, say France, in an Italian DOCG-rated wine regardless of how it tastes, so the grapes ARE a DOCG factor. A few years ago Itallian makers of Brunello wines got into serious trouble putting "other" grapes into their Brunellos. I think they might have handed down some jail time over it, but I can't say for sure.
While it is arguable that "a wine cannot be better than the grapes" that go into it, having "high quality" grapes does not guarantee good wine either. We can agree to disagree on this, but I think it is a lot of money for a boatride.
True, you can make a bad wine from good grapes, but you can't make a great wine from bad grapes. You can zest a wine from c**ppie grapes or add anything else to it until h**l freezes over and it will still not be a great (or even a good) wine... it might get better, but it will never be great.
Many new home wine makers start out with the same old question, "What equivalent commercial price range of wine can I make from a wine kit?".
The answer is of course that the better the kit, the better the "potential" results, IF the wine makers knows what he/she is doing.
For that matter, the same question can be asked of wines made from fresh/frozen grapes. The answer is pretty much the same as for kits - higher quality grapes can produce better wine.
One would have to ask why the Italians are selling these "extra special" grapes, instead of making $50 bottles of wine from them. The same question can be asked about Brehm Frozen Grapes, which can be as much as $275 per 5 gallons of red must.
(If vineyards would consider selling you their superior grapes (which of course they won't), if you did purchase grapes that typically make a $50 bottle of wine, how much would you have to pay for 5 gallons of their must?)
For Brehms, in my opinion the answer is - if you really know how to make wine and you have the proper equipment and environment, if the grapes really are extra high quality (cost $150 to $275 for 5 gallons of must), you actually can make the equivalent of a $50 or more bottle of wine.
There are not really any "special tricks" used by top secret wine makers to make the superior wines; it is all know-how and great grapes. Give a good winemaker a bad batch of grapes and he will make you an inferior wine.
What it comes down to is -
Are the grapes really high quality enough to make a superior bottle of wine?
Do I really want to pay enough to make a superior bottle of wine?
Do I really even care to drink superior wines?
Is there even such a thing as superior wine and what is the definition?
The answers are all a matter of personal opinion.
IMO, I would want several references before I pay $150 for 5 gallons of must and I also would need to have a very good reason why I want to make such an expensive wine, which right now I don't.