ARs aren't expensive at all given their capabilities. You can get one set up for "tactical" use/home defense, buy a $400 stainless bull upper and switch it to a precision rifle shooting 1 MOA or better in a matter of seconds. If you dedicate optics to a particular upper, it doesn't have to be re-zeroed either. You can have "several" rifles all with the same serial # for different purposes. Some days you might feel like shooting a scoped AR at long range, other days you might want to pop rounds at short range using your RDS.
For the casual and advanced shooter alike, no other rifle is as versatile. By purchasing the right accessories, you can make them fit just about any role. Be it caliber, barrel length/profile, rifling twist rate, ANYTHING-it can be just as you want it.