The bedroom is about unadulterated luxury and a nice deep pile will bring the ultimate softness to your toes. Bedrooms are not as prone to thousands of foot steps as the main areas of the home, so you can afford to use a slightly less dense carpet and hence save a bit of money over dining and living rooms.
Remember that most of the time you are going to have bare feet or be in those worn out, but too-comfortable-to-chuck-away slippers so wear and tear is minimal. And apart from the odd cup of tea to kick-start your day, stains from food and drink won’t be such a problem.
Don’t forget that spare bedrooms get even less use and so can make do with a more cost effective, lower density pile than main bedrooms.