Answer: a little… or a lot. What?!!? You were hoping for something a little more insightful?
Okay, then. Here goes. To make it easy, I'm going to make a couple of assumptions. One is that you will be buying a brand, new gun. The other is that you will actually train with it.
On the first, there are many, many good-value guns in excellent condition available on the used market. As with buying anything used, it's important to look more closely at the seller, and hopefully the actual condition of the gun. Anything new typically comes with some kind of warranty or guarantee. Anything used often is sold "as-is," so caveat emptor.
It is always possible to buy a Ferrari -- if you can and if you want to -- but that's not the typical choice of most people. So let's look at four different potential buyers intending to buy one handgun or one rifle, or both. I caution that this is my thumbnail sketch looking at current prices put together about five months ago. Nonetheless, here it is:
As you can quickly see, buying an inexpensive gun, some ammunition, safety equipment, and the bare minimum of locks for safe storage is just a skoche more than $500. And this only accounts for limited range time.
Is that you? If so, go for it, baby! Responsibly owning a gun and having it available in your moment of need is far, far better than having no gun at all. And here's a little secret about training: you can do up to 70% or so of training at home, "dry firing." This means using an unloaded gun in a "sterile environment" (no ammunition in the room, guys and gals), assisted by a kitty-laser-toy rubber-banded to the barrel and a home-made paper target. Doesn't go "bang," but catch as catch can.
Moving on to door number two is Mr. and Mrs. (or Ms.) Average American. Word is lately that the "middle class" in America is disappearing. Nonetheless, if that is you, you'll probably spend around $3,000 to acquire one gun and train with it. Perhaps more, perhaps less, but around there.
The upwardly mobile ("from where?" I always wonder) might spend twice the putative average. And they will be well-armed, well-trained, and happy. Will they be better off? Objectively, yes, to one degree or another. There is frequently -- but not always -- a correllation between higher price and better quality, dependability, durability, etc., etc., etc.
And then there's the money-no-object crowd. They will spend more. Some will spend way more than contemplated here. Though you do generally get what you pay for, there is a point of diminishing returns. I'm reminded of hyper-close tolerances machined into some very high-end guns whose parts are lovingly hand-carried during each point of their cosseted manufacture and assembly. Sounds great, but I don't think it is.
And this isn't just sour grapes from me for guns that will live out their lives perhaps better than I will, served up ammunition by butlers carrying each round on tiny little pillows. It goes to whether micro-close tolerances between violently-moving chunks of steel are a good idea at all. As Henry Ford famously told his engineers one day, "If you don't increase the tolerances for the parts we manufacture, you'll drive me out of business."
When I decided to buy a gun, I called up a
local sociopath good friend and said, "Hey...I want one handgun and one rifle. What should I buy?" He told me, and I did (a Smith & Wesson full-size 1911 and a Sig Sauer [AR-15-looking] semi-automatic 5.56 rifle). In starting out, I spent what I'm calling "Mr. Average."
I may have spent a bit more here and there. Okay: I cashed out my 401k and spent everything. If I run into you at the food line, I'll tell you all about it. Good times.
But if you are trying to get a fix on whether to buy a gun, and just can't quite get a straight answer on what that may cost, there it is. As the saying goes, "YMMV" (Your Mileage May Vary).