There are always diminishing returns issues with tools.... knives, power tools, guns, flash lights.... you name it. You just have to get what you think you will be comfortable with. I carry a small Vic SAK all the time and for the most part, this $20 knife is all I need day to day. But I have more expensive stuff that I like.
We tend to spend more money on stuff we are more interested in. There is an experience issue involved too, but I think there is a happy median between good functionality and cost which I think tends to fall in the $60-$100 area in general but will vary with the particular knife.
I just bought a Rav-o-vac battery lantern for $30. I find them really useful for work in dark places when holding a flashlight is a pain in the butt or the head lamp is just not quite enough. I use them for emergency lighting too at home. I have a number of these lanterns. I buy them for functionality and not particularly weight or looks. They are quite comforting to have available at home or camping.