As to the fines or a warning, it is usually at the discretion of the officer. As for cost of the fine, I think we have established that it varies across the board.
I have only to offer what I do. (Now, new this season boaters, take note. After you have ALL of your safety equipment, this may help you out next year)
At the end of the season, I remove my spare props, anchors, ropes, skiis, pfd's, etc. and they go on a "reserved" set of shelves and closet rod. Then, I take a plastic tote. One that is sufficient in size for what I need. I then remove ALL of my safety equipment from the boat. This is both fire extinguishers, tool kit, first aid kit, flares, registration, insurance info, back-up whistle, fuses,etc. Then, the tote goes on the shelf also. Now everything that I need for the boat is in ONE place and ready to be put back in. Next Spring, tote comes out, everything back in the boat. This may seam a little overboard

, but if I have certain items IN MY HAND that have expirations what better time to check them rather than trying to remember to do it when they are out of sight, out of mind. Also, I know that I have all of the items I need in the boat. (Plus, getting that good deep cleaning in the boat is easier with everything out of it.)
I don't know if this will help all, but it gives me a great piece of mind knowing that I have everything I need, and I can check the condition of every item as I put it back in the boat. If something need replaced, that item is put to the side, in my way, to serve as a "string around my finger

" to get a new one before I go out.
Happy boating.