The Apple monitor will likely have better speakers, and I'm not even sure the others will have microphones at all. Apple also does a better job with color accuracy/consistency, at least historically. There's still a sizeable markup, but it's not entirely for nothing.

Back in the day (~15 years ago), when 4K monitors were unheard of and even Apple's high-end displays were still 1440p, you could get a bottom-dollar monitor using one of their panels (e.g. Yamakasi Catleap Q270) for about a third of the price. However, it came with no amenities, a single connector (dual-link DVI only), a questionably legal power cable, and no built-in scaling. The vendors, presumably to prevent refunds, even asked for your graphics card model before selling it to you, because it wouldn't work with low-end cards. Oh, and there were very few in the U.S., so you were typically getting them shipped straight from abroad, customs duties and all.

We've definitely come a long way.