As with almost any personal property item, supply and demand are major factors (if not the largest factors) in determining value. High demand and little supply usually results in high value, while the reverse is generally true.
There can be huge variations in the value of the same wine from the same producer, depending on the vintage year of the wine. A wine from a mediocre or poor vintage might be worth a small fraction of the value of the same wine from a great vintage.
Wines from outstanding producers, with consistent quality of winemaking expertise and grapes from superb vineyards will almost invariably command the highest prices.
Certain long-lasting grape varietals, such as cabernet sauvignon, merlot, pinot noir and nebbiolo usually produce the most highly valued wines.
Cabs and merlots from Bordeaux, pinot noirs from Burgundy and nebbiolo from Piedmont usually command much higher values than the same great varietals from Chile or Australia or South Africa.
Wine bottles with labels/capsules in pristine condition and with appropriate fill levels (ullage) generally have greater value than stained/torn labels and/or low fill levels.
Wines from the collections of celebrities and famous collectors generally command a premium in value.
The same wine in larger formats (magnums, double magnums, imperials, etc.) will generally have a greater value proportionately, due to the smaller air to wine volume, as compared to a 750ml bottle, which usually translates to longer life.