I'm in the UK, in Lancashire, so maybe a bit cheaper than where you are. But even so, that quote for wood is absurd. My head is hurting just thinking of that price you've been quoted.
We have wood yards/builders merchants up here which are wayyyyy cheaper than the likes of home stores such as B&Q. At a push, for that size tank you could quite safely, and much cheaper, go for 3x2 wood, instead of 4x2. Half inch ply instead of three quarter inch. Typically, aquarium stands are preposterously overbuilt anyway.
You'll still have a stand that can take three or four times the weight your tank will ever come to, as long as you follow the standard build template for aquarium stands (plenty of tutorials on line).
There must be a cheaper way than forking out over £400. Hell, if you were local I'd build you one out of scraps I have in my shed and not charge you anywhere near that.