What Merlin said. Anything done a $50 tune up you should be able to do yourself. Anyone with a little common sense is more than capable of checking tires, cleaning the chain, lubing the derailleurs and adjusting the brakes (you should be doing this on a regular basis anyway). There are countless videos on Youtube to show you how. If your bike is running just fine, it probably doesn't even need a tune up. Now, if your bike is a few years old, it might be worth it to spend a couple hundred to get a full overhaul where they disassemble the cranks and headset and really give the bike at total refresh. The cheap tunes just seem like a waste of money, especially if everything is working properly.