$5000 to $20000 http://www.uipatent.com/
Unknown. I've never seen a patent for sale.
No, they do not have a patent. They have a trade secret. Much like KFC there are very few people who know it.
About £200
too much......
There's really no way of telling. If the product is popular and successful, the value of the patent will reflect that.
It depends upon what the invention is and whether you're making a patent or buying one that has already been granted and in which countries.
If the inventor will be the patent owner (rather than a company the inventor is working for), the fees are 1/4 what they are for companies. The complete US patent fee schedule is linked below.
Up to 500 USD
It would be smart to get a provisional patent first. They are inexpensive and can be useful for two reasons. Reason number one, they are a patent an will protect your idea. Reason number two, it is much faster to acquire a provisional patent than it is to apply for a registered patent.
Before you file for a patent, you'll need to contact a patent attorney. The cost for attorney time alone is usually around $1500. You'll need drawings of your idea, which run $100 - $150 per page, and a fee for the actual patent itself.
Depends a lot on what type of rifle, patent alone doesn't cut it.
send me a picture of the rifle