If you shop around you can get a good 1200 watt inverter for less than $100. I have a couple of them and they are good to have around in an emergency. You are not going to be able to run any appliances with it, but it is good for charging any batteries, and powering floodlights, a TV or home computer or even a microwave oven.
I wouldn't recommend any inverter over about 1500 watts. You will not be able to power it off of your car battery without heavy cables and even then you will have to keep your engine running. If you are looking for 2500 watts or more you are better off buying a generator.