1 cubic yard will cover 144 Square feet to a depth of 3 inches. So you need just over 2 yards. I have no idea how much sand weighs but it is heavier than topsoil. topsoil runs about 2 tons per yard. so even with that you need 4 tons. sand is even heavier so the 5 to 6 ton could very well be right in the ball park. I do wonder, If you where not going to believe the guy, Why did you even bother asking him?