Surprisingly,...

the real cost is not obtaining the patent in the first place, it's defending it against infringers if (repeat: if!) it's a real moneymaker. The costs for all the patents I hold were borne by my employers at the time, to whom all rights were assigned by me, per my employment agreement.

Bruce, the latest example I know of is maybe 3 years old. It was a friend's patent for a very useful modification to a sailboat's sail. His cost was about $15,000 for the patent, mainly legal costs, of course. So far, I don't think he's made any money with it, although he had several people interested in the invention initially. Also, I don't know of any infringrement attempts.

Your best bet is to get a rough estimate from a patent attorney. Also, I'm pretty sure that if you file a disclosure of the concept with the Patent Office, you reserve the exclusive rights to file on the concept within two years, but please verify that for yourself.

"1% inspiration, 99% perspiration!"

DTW