I play 600 credit, L+85 Nike 20 XI-X Vapor balls that have a Durability rating of 2.5, which is 120 hits per ball.
Putts don't count as hits (unless you take a Mulligan in Practice mode).
Par is set for an 18 hole par 72 course for 2 putts on each hole, or 1/2 of par, leaving 36 hits of durability a ball loses in 18 holes.
So assuming you shoot par and make 2 putts per hole you use up 36 hits per 18 holes.
120 / 36 = 3.33 18 hole rounds per ball x 3 balls = 9.99 rounds per sleeve of balls.
Many serious real world golfers use a new sleeve of balls (3 balls) just to play 18 holes. All the balls left at the end of the 18 holes become practice balls and don't get used for a scored match ever again.
So from that perspective - WGT ball are cheap, and last on hell of a long time if they are't hit OB, in the weeds, or in the water.