I believe US $ Bitcoin price should be that of gold for it be financially stable.
The "price of gold" is the price for 31.1 grams (troy ounce).
There are like 5.7 BILLION troy ounces of gold and only 12 million bitcoins. 1 bitcoin corresponds to ~15kg of gold (12mn bitcoins vs 180.000.000 kg above ground gold) in terms of scarcity.
In terms of rarity, even the 1oz gold eagle coins issued by the US Mint are more plentiful than bitcoins. And that's just one bullion coin, for a certain weight. There are tens of gold coins, weights, different countries, different years etc - making for hundreds of million of ounces in coins.
Given that:
a) As a collectible, Bitcoin is the first decentralized coin with high rarity (like saying "the first coin minted on metal" - but that's the first coin which was digitally minted so to speak)
b) Bitcoin is ahead of gold in scarcity / rarity compared to gold
c) Bitcoin is more difficult to mine than gold
d) Bitcoin provides a service of online payments which is an enormous business of over >100bn $
e) Bitcoin is ensured to increase in fiat terms due to the tremendous increase of fiat monetary supply - and that's especially true for 4/5 of the countries around the globe which have weaker currencies than the USD or EUR
f) Bitcoin, unlike gold, is not subject to paper manipulation and fractional schemes that have leverages like 1:100
g) Bitcoin can be "squeezed" to very high prices with a few hundred thousand to a million BTCs demand (because the supply is simply not there to cover such demand)
...it seems that it has all the fundamentals in its favor to reach 5-6 digit prices (yes, 6 digits as in XXX.XXX USD). Whether it will or not, is dependent on people's perception of how much it's worth.