Many photographers want an expensive lens that will deliver poster-size photos but in reality, how many photos make it to that size?
The answer is very few. The cheapest lens that will do the job in hand is obviously the "best buy", but if it misses the target then it's not even worth anything. Sometimes nothing but the best will do - which is why you see sports photographers with their umpteen thousand pound lenses. Yes, a cheap lens will occasionally get a winner, but a professional covering an event needs to get that winning shot significantly more than occasionally.