How much to give at a wedding as the best man?

I was thinking $300. For context we are life long friends, I had to rent a tux, hotel for 2 nights for the wedding, and planned/attended a 2 night bachelor party where we split the cost for all the of the grooms expenses. I am bringing a plus 1 to the wedding. The couple is not the type to be upset about the amount they receive and is just happy to spend the day with friends and loved ones. Is $300 too little or is it a fair amount? I have no clue what they paid per plate.