Now you can apply for a patent, want to sell it to others, or charge a name on the patent. I wonder if this is illegal? How much is the charge?

Legally speaking, once you do this, there will definitely be the risk of patent ownership disputes, and more seriously, it will constitute the disclosure of trade secrets, and there will be civil and even criminal liability.

In fact, this is feasible, but you must act in secret.

The fee is only for technical proposals, plus the patent writing fee at most, which is not too high, and each article is capped at several hundred to one or two thousand. Unless your technical solution has great market value, that's another matter.

Companies with sufficient funds can buy ready-made authorized invention patents in order to apply for projects, and the prices range from tens of thousands to hundreds of thousands.