I need my knife for all the usual stuff, cutting string, plastic, cardboard, screwdriver!
For a really good knife I don't mind saving up, but I would say I'm looking to spend around $200.
Most here will tell you not to use a knife as a screwdriver. It's a good way to break off an expensive blade. (most steels with good edge retention are at least somewhat brittle) A swiss army knife would work well for that but it doesn't have great edge retention. Of course, they are easy to sharpen. I suggest you look at something like a swiss army knife alox cadet if you need a screwdriver. If you want longer edge retention AND a screwdriver you may need to carry two knives. I'm carrying a SAK and a Spyderco Caly 3.5 with VG10. I like the balance of edge retention and ease of sharpening on the VG10. Other steels keep an edge much longer but are much harder to sharpen.