I bought a Tauras 1911 several years ago that I've been quite satisfied with at $600.

I bought a compact RIA in .45 acp and it's been a fun gun to take to the range. Smooth action and well made value is what comes to mind. Another RIA model is the Citadel. Those are supposed to be a bit better quality than the regular RIAs and can sometimes be found cheaper.

If it's strictly budget the ATI 1911's would be a solid choice but for like $200 more I'd go with a springfeild

Taurus makes a 1911 in the $500 range. I have no personal experience with it.

I have the Rock Island in 9mm and I cannot tell a difference in accuracy or reliability between my other 1911's ....Sig , Colt , STI

The very best budget 1911 I can recommend is the Springfield Armory Loaded model. You get a forged frame and slide, mine was very well fitted and tight....shoots one-hole groups, Trijicon night sights, well fitted control parts, attractive Parkerized finish that is very durable and not silly legal script etched/stamped on the slide of your gun....simply the serial number, model type and closely looking crossed-cannon logo. My gun was bought in early March, 2017 and came without their interlock system so I was able to use the mainspring parts for a drop in magwell guide mainspring housing from Smith & Alexander. It took all of five minutes to do. I'm very pleased with my Loaded.

I picked up a rock island armory full size 1911 for $549 recently. G10 grips, skeletonized hammer and trigger, cerakoted. So far I absolutely love it. Great pistol. If your looking for a decent budget 1911, rock island armory has a lot of decent ones, Taurus pt1911 I've also heard good things about.

If you want to buy American, I would suggest a Springfield 1911A1 GI model. If you don't mind an import, I would get the same from Rock Island. They bought a lot of the colt tooling after WWII, so their base model 1911s are not too far off what would have been used in 1944.

This one is a good value and reliable. Under $600 at Bud's.
Magnum Research DE1911GR 1911 GR Model 45ACP 5.05"
Here I am shooting one in 4.25 " Commander size. youtube.com/watch?v=1n2I2k0RT3c

Rock Island.
Made overseas, fit and finish is usually less than perfect, but they run reliably.

Dan wesson gi model

One of my first pistols was one of the budget 1911's, made overseas for in the $4-500. At first I loved it. But it went downhill very quickly, and eventually became a paperweight. In my Opinion, it is absolutely worth it to spend an extra $1-200 and get one of the bare bones 1911's from a reputable company. Springfield and Ruger have some decent deals here on Bud's. But, I have heard a lot of good things about the Girsan pistols which would fit in that budget category. Mine was an ATI by the way...