1440p costs more than 1080p because it has around 78% more pixels, and as a result costs more to manufacture. 1080p is still the standard resolution for monitors, while 1440p is a premium resolution, so you're not likely to find it on low-budget monitors that are designed with low cost in mind, at least not for a while. IPS is also a more premium display type, so that adds to the cost as well, and of course it costs more to make larger screens. The same goes for features like high refresh rates, if you're interested in those. The prices will undoubtedly continue to slowly work their way down over time, but I suspect it will be a while before there are 27" 1440p IPS displays for under $200.
Edit: Assuming you're referring to US dollars. It might help to list a currency, rather than just a number. : P