What is a reasonable price to pay for SEO for my website to get in the top 5 rank on google for keywords like "Watch free movies online"
I hate to answer a question with a question, but do you know what is involved in SEO? Search Engine Optimization is very complex and in my experience I have seen many business professionals waste a lot of money on SEO only to see that their site has had little to no movement toward the first page of results.
Depending on your geographic location, your keyword term may be impossible to get you to the top 5 rank. I would consider looking at SEM (Search Engine Marketing) and researching keyword phrase costs in your marketing area. You may find SEM to be more beneficial and cost effective.