It depends on whether it's new or used and which model. In general, Taurus handguns range between $400 and about $700.
$500.00 is a good price.
45
It depends on several factors, and it is too broad of a question to answer.
M1911 .45 cal
100-300 USD or so
It depends on what brand and what kind of shape it's in. It could range anywhere from a few hundred dollars to a couple of thousand.
I don't know if it's the smallest, but the Kahr P45 is pretty small.
20 dollars and one hell of a night. if you cautch my drift.
50-200
I would pay $1000 for this Pro Conceal .45 acp!
If your question is can citizens of the US own a .45 cal handgun, the answer is yes. MOST of the US does not require a permit to own a firearm, and even the areas that DO require permits do not ban the .45. In some countries private citizens may not own a handgun in a military caliber, but the US does not follow that practice.
100-400