I wouldn't set up a large tank without one. I have 2 of them for my 400g. Out of everything you see for sale used, you hardly ever see a wavebox and only if the person is getting out of the hobby for ever. They really are that good.

And as to the cost, they aren't that much when you consider what they do. For $550 it moves every bit of water in your tank every second. Compare the price to the fact that I also want 2x Tunze 6100 and a 7095 controller will set me back about $1,400 after taxes.