The short answer is that it really depends on a lot of factors. The USPTO does maintain an extensive 'Fee schedule' on its website, so you can see all the potential fees that may be included in filing for a patent. There are discounted fees if you qualify for micro-entity status, and there are a few programs that assist inventors with finding pro bono patent filing assistance.
If you would like further assistance navigating patent resources, please reach out to the PTRC Representatives via email at lib-ptrc@osu.edu.
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