The standards depends on the acquisition. It's what you're doing that driver's what you pay for it. A few examples:
A losing operation might be worth the fair value of its assets.
Acquiring a related entity customer list might have that value.
Buying out shareholders who are retained in the business is different from buying out underachievers or malcontents.
Businesses that have been and will be profitable typically buy on a multiple of profits. Loss companies often buy out some of the loans that a shareholder put in.
One substantial owner might want only the customer list and not pay salaries to the other shareholders.
The other shareholders depends on their salaries and might be willing to take little to nothing to keep their jobs for a year or two. Or they can be bought out for 6 months pay and unemployment.
I can think of a number of scenarios that drive value paid. Your specifics, including ability to pay, will drive what will be paid.
I am reminded of a father selling his half interest in their two bay car repair and used car sales business to his son. $500 per week was what Dad wanted, the son agreed to and I thought was way too much. The deal lasted 17 years. The son paid for 14 and stopped paying.
I couldn't be specific in your case, but your deal will follow its specifics. If you want to be rid of your other owners, plan to pay them something. Retaining them suggests low buyout with continued employment.
Positive feedback is appreciated after review. I'm PDtax.