A 4K 40” screen has similar dot pitch and is smaller than a pair of 27” 1440p screens. The main advantage is it has no bezels so it’s more flexible.

Also, many TVs are 60Hz IPS displays, but you have to do some research to find ones that display in 4:4:4 color. After that the main difference between the two is the firmware on the device, some things like VESA power saving work differently.

TVs can be cheaper because they have larger economies of scale than monitors. It doesn’t have much to do with the underlying technology.

It seems like you don’t know as much as you think you do about display technology.