I think the “practicality” of a .50 BMG largely depends on where you live and what you expect to do with it. By it’s very nature my Barrett M82A1 is not a particularly accurate rifle. Any short recoil semi-auto rifle where the barrel recoils 1/2 inch is not going to be a “tack driver”. It’s no where near as accurate as my Begara. As far as I’m concerned, the Barrett is really just an expensive toy; just like a 717 HP Dodge Hellcat or a 234 HP Ducati Superleggera. Many of the people who own these toys don’t use them on a 1000 yard range or on the track, but they still can be fun when used on a 100-200 yard range or on the road A .50 BMG can be a lot of fun if you have access to a 100-200 yard range that doesn’t mind you using API rounds to blow various things apart. Granted you don’t find many of these rages in eastern MA, but they do exist in western MA and southern NH. Or if you own enough land, you can do it “in your backyard”.
If you want to do long range accuracy shooting, you’d be much better off with a bolt action (in many of the long rage calibers). If you do want a semi-auto .50 BMG that offers decent accuracy, you’d be better off with a Serbu BFG-50A, which has a fixed barrel and uses a gas system rather than a short recoil system.
Barrett M82A1 practical? For most of us, not really. But if you can afford it (and that IS a big if), you can own one just for the fun of it.