An important element that may need to be clarified is the "cost of filing". Of course there are the PTO fees that need to be included, of which there are significant discounts for small and "micro" entities. But there is a difference between drafting and filing the patent application and prosecuting the patent application. Prosecuting the application is where a skilled patent attorney (or patent agent) is worth the investment. Once the application is submitted there are "Office Actions" that need responses. This is typically where the USPTO examiner rejects your invention. How one responds to these office actions will determine if you are issued a patent and how broad or narrow the claims.
One cost cutting strategy that I referred to above is to use a patent agent. On some occasions, a patent agent with a lot of experience with your invention, exercise equipment, may serve you better than a general patent attorney.
And of course, being a professional patent searcher, I'd suggest a good patent search before you head to attorneys. For a fraction of the cost of filing a patent you may learn that your invention is not novel or considered obvious in light of the prior art and a patent may not be the best path forward. The other side, a good patent search may provide you with information to improve your invention, increase enforceability and value.
Keep asking questions, this list is a great resource.
Gilman Research Services