Compared to copyrights or trademarks, patents cost an arm and leg. Both the costs associated with filing the application, and the legal fees for patents far exceed those for trademarks and copyrights. There’s a good reason for that: not only do patent applications take more work to prepare and examine, the protections that you get from a patent are more robust than from a copyright or trademark.
The right to a monopoly for your invention – to exclude anyone else in the US from making or using it – is a powerful right.
One way to keep your costs down is to file a provisional patent application. For this style of application, you file the figures and disclosure without a set of claims. This filing protects your priority date for one year, and reduces the costs to prepare and the cost to file the application.
However, this provision application will not be examined, and a full application will have to be prepared and filed within one year if you want to pursue the patent.