Cost of modern warfare and logistics

[mr friendly guy]

Ok, I couldn't fit what I wanted to say in the title, but my question is, does the high cost of running a modern military make it almost prohibitive to invade another nation of even somewhat less military and financial capability? For all scenarios assume (unless otherwise stated) the invading nation either wants to make the land a colony like the age of European colonialism or to replace the government with a more friendlier one, and give it the means to maintain its rule. Assume for a moment due to an act of Q, both the defender and attacker can continue trading with other nations as long as goods can still reach via some other source, ie sanctions are not enforced on either country by third parties.

To elaborate further, modern equipment as well as costing lots of build, also costs a lot to simply maintain. The F-22 cost a few hundred million per plane, and requires obscene amounts of maintenance hours. With the higher price of oil it becomes more dearer to run ships and planes, not to mention more expensive to run the usual economic activities.

Now obviously tech differences can be a factor. If through an act of Q, ancient Mesopotamia appeared in the place of Iraq during the war with Iran, the latter would be able to occupy it and set up a puppet government simply because of the technology difference in weapons and logistics, even though their military would cost much more to run. But how likely is that to be repeated, if the defending nation is say, 10, 20 or even 30 years behind in technology and say 1/10 th of the GDP of the invading nation. Will they still win after resorting to Iraq style insurgency and asymetric warfare, or can they hold out like the Guomindang did during WWII and have parts of the country occupied, but the war essentially grinding to a stalemate where neither sides lines moved much, until the attacker is unable to fund further attacks.

Is it possible for say a nation, like Iran which is economically and technologically inferior to the United States simply be able to outlast the latter until the financial costs become too high (lets just assume the human cost to US soldiers is minimal and within predicted losses). Or to put it another way, can they outlast until the US runs out of money.

If the US being the holder of the reserve currency can simply print its way out of the problem, what about other states with modern militaries like the UK. If the Falklands residents and military infrastructure magically teleported into the London, could the UK still fund a force to retake the place, given the high costs of building an aircraft carrier and their financial situation.

I am hoping the discussion not only takes a look at the technology, but also the costs of running militaries, as in my observation, people discussing military vs threads tend to focus on the tech, rather than the economics, which I consider also important.