The Elusive M1911A1 Pistol
The least expensive but still durable option is a Springfield GI45. Swap out the goofy US grips for genuine GI grips (about $15) fit a genuine GI thumb safety, ($10) and Bob's your uncle. If you want to get fancy, swap in a GI mainspring housing to get rid of the ILS. Take a quick look at this pistol. This gets you into the game for $600 or so, including taxes. There are cheaper guns available, but they are cheaper.
Next up is a shooter grade M1911A1. These can be Colts, Ithacas, Remington Rands, or occasionally Union Switch & Signals. Sistemas fit in here too. These are the real deal historical guns. What you want is a pistol with enough finish wear or mixed GI parts to take it out of the collector's realm. These start at $600-800 and go up as high as the seller thinks possible. Know your stuff here. Experts and good info are available at the USGI section of the 1911 Forum. Register and learn. Read up on The Sight M1911A1 for good info.
Next will be the Colt M1911 or M1911A1 repro. These start at $1000. Occasionally you can find one for less, maybe $850-900. People think they are instant collectibles. If they are, all Colts are. Buy one and shoot it. These are fairly close to the real deal. Swap out the trigger on the WWII repro with a genuine GI trigger. The M1911 is fairly close on the small parts.
Finally, there is the M1911A1 itself. Expect to pay $1500 and up for an original Very Good unrefinished condition Remington Rand, Colt, Ithaca or Union Switch & Signal M1911A1. The good thing is it will hold it's value, and indeed become more valuable if you take care of it and just shoot it. If you want a Colt M1911 (not A1) in this condition, think $2000. These pistols are one of the best investments in the gun world, if you can afford one. Again, be wary of fakery, and know your stuff. A year or two spent on the USGI forum reading and educating yourself is beneficial. If you get into this area, be aware that just about everyone gets burnt once, some multiple times.
Remember, always buy the gun, not the story. Money spent on books will be recouped when you evaluate a pistol. Use my Pre-Owned 1911 Checkout to check out any prospective purchase. Lastly, have fun in your search.