In this photo taken on Tuesday, Nov. 25, 2014, a sign advertising the price of gas towers over Interstate 80 in Omaha, Neb. The cheapest gas in half a decade is expected to entice more Americans to pile into cars, trucks and vans for their Thanksgiving journeys. (AP Photo/Nati en

After last week's dramatic plunge in oil prices -- prices for U.S. benchmark crude have fallen more than $30 a barrel since late June, and were most recently at around $ 68.50 per barrel -- a natural question arises: How much lower could they go -- and where will that leave nationwide gasoline prices?

As of today, according to AAA, the nationwide average price for a gallon of unleaded gasoline is $2.77. But given the recent plunge in oil markets, "we expect gas prices could drop another 10 to 20 cents per gallon in the near term as retail prices catch up on the steep declines in the cost of wholesale gasoline," says AAA spokesman Michael Green.

So, nationally averaged gas prices approaching $2.50 per gallon are hardly a radical thought.

But what about $2.00 per gallon? The last date on which prices were below that level, says Green, was March 25, 2009 -- deep in the Great Recession -- when nationwide average gas prices hit $ 1.99. From late November 2008 through March 25, 2009, prices were below $2 per gallon, according to Green.

The number one factor affecting gasoline prices is, not surprisingly, the price of oil. According to the U.S. Energy Information Administration, the corresponding WTI crude oil prices during those months of the Great Recession were as low as $33.87 per barrel at one point, and often under $40 per barrel. For Brent crude, whose price actually appears to contribute more to the ultimate price paid by U.S. consumers for gasoline, you'd need a change from about $70 now to about $50, according to Brian Youngberg, a senior energy analyst at Edward Jones.

Source: Federal Reserve Bank of St. Louis.

The U.S. Energy Information Administration goes by a general formula that "if every $10 drop in the price of a barrel of crude oil is fully passed on to consumers at the pump that would equal a 24-cent drop in the price for a gallon of gasoline," according to spokesman Jonathan Cogan. So based on these kinds of considerations, to get down to $2.00 gasoline, we still have a pretty long way to go.

That doesn't mean it's impossible -- just quite unlikely, in light of the other market mechanisms that are likely to kick in as prices go lower. According to Edward Jones' Youngberg, with prices in the low $2.00 range, global demand would naturally increase. And in the oil markets, as prices continued to tumble, production might also be cut, whether by OPEC or some other major players -- again leading to higher prices.

$2.00 per gallon gasoline is "at least possible,"says Youngberg. "But if it did get down to there, I do not think it would last very long."

One important contributor to low oil prices right now, the boom in U.S. shale oil production, might also shift if prices fall far enough. "There’s a self correcting market mechanism," says Paul Bledsoe, a senior fellow on energy at the German Marshall Fund. "Much of the shale oil now being produced has a production price higher than $50 per barrel, and so, to the extent that oil prices continue to fall, at some point production will slow, and that will happen both in the US, but also globally."

It is important to bear in mind that gas prices also vary by region -- they tend to be lower in the U.S. South, Southwest, and Midwest -- and season. Due to refinery maintenance, there tends to be less gasoline supply in the spring, and prices are often higher, explains AAA's Michael Green. In the winter, when people aren't using their cars as often, prices tend to go lower. This also suggests that the low prices that we're seeing now may not be around for very long.

But then again, the near term picture is, most of all, one of uncertainty.

"Think back to June, if you had told anyone that oil would be below $ 70 later this year, no one would have believed it," says Edward Jones' Youngberg.