Barring antiques (which cost more due to sentimentality and rarity), do weapons in the real world scale in cost and utility as magic items do in D&D?
In the real world, you can buy a pistol that costs $100. It's dinky, but it works. That's a normal sword.
If you want a quality pistol, you can easily buy one for $1000. That's a +2 sword.
If you're a gun aficionado, you could even buy a custom-made pistol with specially made bullets, a personalized grip, the finest and lightest scope, and some amazing technology to kill any kick, and spend $10,000. That's a +4 sword.
But the only people I know of who have $100,000 pistols are drug lords of international cartels, and I don't think this thing is a +6 weapon:
I dunno, maybe magic items in D&D cost too much. Or maybe Olympic shootists and elite mercenaries do spend hundreds of thousands of dollars on a single gun.
Either way, my main problem is that a lot of 'epic' magic items are boring. Oh, so this sword is mathematically superior to that one? Wow, that's impressive. But I'm fighting gods. Where's my sword that can cut down a forest in a single swing?
D&D characters spend irrationally. If I have $300,000 dollars, I'm not going to own three $100,000 items and nothing else (one to hold, one to wear, and one for my neck). I'm going to have most of that invested or in a bank, and probably splurge for a single $50k item, and then have a variety of smaller things.