Here's an article that states the average 510K is $24M. http://www.mddionline.com/blog/devicetalk/how-much-does-510k-device-cost-about-24-million
It really depends on what other devices are already approved similar to yours because you can sort of piggyback on their work. That is what makes the 510K cheaper than a full scale approval.
I just noticed your comment about $40,000. I can't imagine that being close to enough to run clinical trials needed for approval. I've worked on regulatory submissions for over 10 years at major pharma and biotechs including overseeing regulatory documents for approximately 1,000 clinical trials including working first hand on several hundreds of trials and on submissions.
My suggestion is to begin talking to device industry people to get their input on costs.
Regulations are very strict and you need extensive documentation, investigators, clinical trial monitors, statisticians and numerous other staff.
To get FDA clearance you will need VC investors willing to invest very substantial amounts. I have not done a 510K, but full scale FDA clearance costs $1billion. The 510K being less, I would still expect you are going to need in the $100M range. But you should be able to research and network with other people who have succeeded with device approvals.
You may be able to obtain grant funding via NIH to begin work on the product.
This is not the type of company that can be self-funded so you need an extremely convincing story to get investors to buy-in without a marketable product, which is not easy.