My mechanic recommends a high quality chain and cheap sprockets. He says that way they wear out together and you just change the whole thing every time. I have found this to be true at least once with a Regina chain and Brand X sprockets, not sure what, actually.
However, the last time I installed a new set of chain and sprockets, I also installed a Scottoiler. I now have 8000 miles on this set and have adjusted the chain i/2 turn in that amount of time. I am currently in Mexico and I recommend this device wholeheartedly. The cost is about the same as a set of chain and sprockets and at this wear rate, I believe if you keep a bike long enough to buy one extra set you´ll break even. Any longer that they last is lagniappe.