I'm not really interested in 4k at all, and they are a bit expensive. And at those prices, I might as well buy a TV instead. :/

They're really not that expensive, but regardless any 30 inch display is going to cost more than $300 and a 1080p monitor at that size is kind of pointless because the pixel density will be terrible. The highest I would go at 1920x1080 would be 24 inches, maybe 27 but still 24 will look better. If I were buying monitor right now I would personally pick up a 24 inch 4k display for around $300. The pixel density is insane.

Depends if his gpu will be able to run 4K.

Even if it can't quite, 1080p on a 4k display looks just fine since it will scale perfectly. Regardless if you're spending $300+ it makes no sense to get a 1080p display.