Any one can bypass a patent if they violate the law and international agreements. China or a US company.
Getting a company to sell with royalties a unique and great device won't happen in my opinion. At least for long.
If you don't have a patent then the company that you license to sell your device will get a patent on it for themselves and then cut you out of the equation in a completely legal maneuver. (It happens more than you would think, copyrights have the problem as well)
Your so called agreement for royalties will not be enforceable as you won't hold the rights to the device, they will. On top of that I don't think any company would sign a license agreement with you without a patent as they would tool up for the production and then another company would start building the same thing.
Don't know what expensive is to you but many little inventors get patents and they are not rich and some of them hold a lot of patents.
I have no idea if the below statement is accurate but a quick search on line yielded the following:
The basic filing fee for a design patent application is $760 for a large entity. A small entity's fee is $380, while a micro-entity's fee is $190. If you hire a patent lawyer to assist with preparing documents and filing the design patent application, the cost could be around $1,500-$3,000.