Thus the important ratio might be "loaves per gram" or something more like that, as if it goes sky high in dollars, what you really mean is that dollars are useless, and loaves are also sky high in dollars, right?
...exactly, it is not that gold gains hyperbolic in value in times of troubles, it is the opposite way around - it is almost the only monetary equivalent that will largely HOLD its REAL value (and thanks to supply/demand laws, it will actually increase it's REAL value).
Just look at the historical monetary collapses, black market always thrives (man, I might even find my life experiences from communist country a life-saver in the future - although not so very happy to go back to "good old days"), and the "official" currency becomes worthless. Usually, some foreign currency took its place for all real-world (eg non-government approved/related) transactions. In Poland, it used to be a Dollar/Deutsche Mark - obviously illegal, but if you wanted to buy something quickly, for example a car - if you had them, you were sorted. If you haven't had them, well, tough luck, you were stuck in the queue with all others Kowalski's, waiting in the official waiting lists, for everyday's items, that you could eventually (when your turn happened - usually years and years of waiting for a car, or more than 10 years for a flat, forget about a house etc) buy for an "official" price (that was ridiculously low, in real life, if you decided to sell it off right away), using "official" currency (that was basically worthless, and exchanged immediately for ANYTHING that had some real-life meaning, if you happened to came across it somewhere - to be bartered later on with your friends/family/neighbors)
But in the current situation, there will be little to none trust in ANY currency after they start collapsing one after another (or all of them together), what's left, as universally, ALWAYS recognizable medium of value?
What is really important, how would the ratio of exchange look like for other items that you would like to trade for: for example, OZ/acre of arable land? Will it go up against land, or not? Against everyday items?
I presume it will - for one reason, there will be probably a HUGE investment demand (and I mean INVESTMENT, not trading here), and gold, unlike farmland, you can easily sell in as small hunks as you wish (I assume you don't own a 400OZ bars), whereas a farm, you have to sell as a more or less whole, and there will be preciously little people who could afford one and/or a credit - thus sending land prices down, IMHO. Regardless that people would starve and fight over food, actually, it might very well happen, that a lot of farmland will lay wasted (dependent on mechanization, not labor, plus no affordable oil to work it, and add foreclosures on heavily indebted big corporational farms etc.)
Back to the OP - correct me, but the "windfall tax" is only applicable when you sell your gold (and officially, brouhaha), am I correct? I wouldn't be too much concerned, I would just keep the gold. If the "new currency" is to survive, it will not leap back too much against gold, if it is to collapse as well, hmm - we are back to square one. Assuming you don't need to eat away your gold, just keep it. If you do need to eat it away - sell as little as you can in the black market, and make your living of it. Just be very, very careful. And try to get by with silver first, it doesn't draw as much attention, is much less risky, I suppose.
If you want to "eat away" a large chunk of your gold at once, and make some killing on it - let's say, buy a farmland etc. (I'll probably try to do something like that, as currently I am not prepared very well, apart from general DIY/handyman skills, some good few years of martial arts under my belt (unfortunately, catching the bullets was still in the higher class than mine), and few chests of hand/electric tools) - I cannot imagine, that any seller would oppose to be paid in gold, in such a case of a general turmoil, actually you might be able to secure much better deal, if you offer to pay in gold - thus you don't need to "sell" your gold for fiat, just bypass that step and go to the seller right away. No windfall taxes to pay other than capital gains/whatever applicable I guess, which you should be able to pay easily with the remains of your gold/silver sold on the black market. Again, you were not supposed to own dollars back then in the communist block (it was just illegal), but it never stopped them from being broadly accepted (and quite often, the ONLY accepted currency) in big transactions between citizens. Same will apply here, with the difference of names - dollar becomes a fallen fiat currency, gold becomes a dollar of yesterday (and one Iron Curtain away).
Regards,