Lenin

I've wondered the same thing. It would be very hard to find out.
Certainly MOST of the salt is in the liquid but it's dried beans that are soaked in the salty brine so a goodly amount is sucked up into the beans.

Whatever the count, it's wise to toss the beans into a collander and rinse with water before using.

To get around this situation and save money to boot (but not time,) buy a pound of dried beans and soak overnight in water. Same beans, no salt...and cheap as cheap can be.
Don't add any salt to the water because the salt slows down the soak a lot...any salt you really WANT should be added after the beans are cooked.

Remember to cook long enough. If you are used to using canned beans they are pre-cooked, dried beans are not.