If you are careful with your linens, launder them properly, and personally place value on having fine things, then I do think that high-quality linens are a good investment. My personal buying habits are such that I prefer to have high-quality products that I only have to replace every ten years or so. I hate shopping.

If you don't want to have to worry about staining your sheets, then go ahead and buy the cheapies. You won't feel a tremendous difference, but they will start to look grotty after a few years.

The one Rule is always buy 100% cotton. There are some newer rayon-like fabrics made of bamboo- that will feel good too. Avoid anything made of plastic (e.g. polyester)

As with any consumer product, you are paying for a mix of brand/design and fiber and construction quality. Unfortunately, it is the buyer's responsibility to know what they are paying more for.

Companies that trade on their design and stylish image will usually also have a product with high fiber and construction quality. These are the most expensive products. You are paying for both style and quality.

Certain companies put out products that are medium on quality, but don't have a reputation as stylish. They usually don't buy ads in premium magazines. An example that comes to mind is L.L.Bean, and I haven't personally looked at their linens, but my experience with their clothes is that they use fairly good material and have pretty good construction.

And then there is everyone else...some pretend to be luxury but use shoddy materials, and some don't even pretend to be luxury. I see these for sale by street vendors and in dollar stores. My personal rule of thumb is that if a price seems too good to be true, it probably is.

Oh, and regarding thread count- at this point the whole thread-count thing is mostly a sham. The thread count refers to the number of individual threads contained in one inch, and so the idea with a high thread count is that the threads are so fine that they can fit more in an inch, and so the fabric feels smoother to the touch. The industry, especially the low end, has twisted the rules and straight-out lied about their thread count in order to seem better. Read this for more information: http://www.linenplace.com/product_guide/truth_about_thread_count.html