There's many things it can be, things I would check are the chainring bolts, if they are loosening they can make clicking noises. Or, chain may simply be hitting the rings as it goes around.

It should not be expensive at all to change the chain, that's ridiculous! If you follow a video you can do it easily... all you probably need is a chain breaker, a new chain, a zip tie and a master link (these usually come with the new chain).