I've put together a few budgetary quotes on largeish aquariums in the past few weeks actually, just to add to the discussion here. One of them was 100 gallons, 36" tall, 15" deep, and 48" long (yes, wierd size). Glass was going to be $1200, acrylic would be around $800, or even less if he went to 33" instead of 36". Glass would weigh 310lbs, acrylic would weigh 168. Obviously the acrylic makes more sense.