In four words: use your common sense.
If AVATAR is a very high budget film, BURIED is a lo-budget film, then you can probably make a pretty accurate guess at your own project's budget.
Is it period?
Does it feature lots of exterior shots and either complex CGI or crowd scenes?
Does it feature lots of action?
Is it full of speaking parts?
Does it feature scenes at sea or featuring child actors or night scenes which may restrict shooting hours?
Again, don't stress about this, just use your common sense. It'll be fine...