Okay, you actually asked three different questions here, so let's break each one down.
- Are these online course certificates actually recognized by producers, agents, directors, etc., or will having this on your resume
make no difference at all?
To be quite honest, when it comes to selling a screenplay, you are probably going to start with either an agent or a producer/publisher. They will not care one way or another what your educational background is or what your resume looks like. The only thing they are going to look at is your screenplay, so the certificate/degree in and of itself will make no difference to them.
Having said that, though, the educational experience may give you the tools that you need to be able to craft a better screen play that will draw their attention in the first place. If the classes help you improve your writing or help you to develop a better product, then that in itself will improve your chances of successs.
- Are they worth the money? They range in price between 4 and 5 thousand dollars.
Is any education "worth the money"? Again, it comes down to whether or not you believe these classes will help you improve your writing or help you to develop a better product. I would argue that anything that helps you improve yourself is definitely worth something, but each individual has to decide for themselelf just how much it is truly worth.
Look at the classes that are being offered and try to evaluate where you believe you will benefit the most. If you feel that you already know everything that is being taught, then it probably isn't worth the money. However, if you see that there are topics that you are not familiar with, then you have an opportunity to improve yourself, and that has worth.
- Do they help you find avenues or contacts to help you sell your work (Assuming that it's very good and you are motivated)?
I would see this as very unlikely, esepcially considering that the other participants in the class will be trying to accomplish the same thing as you, and that is to sell their own screenplays. You will be in a community of participants who are all competing against one another for a common goal, so the chances of anyone helping you to sell your screenplay are going to be very limited. Your interaction with the instructors will be very limited, and their focus will be on conducting the class. If you are an outstanding student with exceptional talent, then they might be able to recommend you to someone, assuming they have connections, but I wouldn't take any of these classes just for that reason.