If they want to do that, they will do it anyways. Look at it this way, you want a cheap patent, so how can you defend your patent? Do you believe that having a patent makes you immune from someone else copying your idea? If you get your patent, and start making the product, and they want to copy it, they will! Then, when you see that someone else is making your product, you will what? Hire a lawyer to sue them? Hope you saved enough on that patent application to pay for that lawyer, he's gonna be 10 times as much! Also, your cheap patent lawyer better have crossed every T and dotted every i or the court will probably find for no infringement.
These are the worst case scenarios, but if someone wants to screw you, they will. Unless you have the money to defend a patent, it means nothing.