Hmmm shouldn't you do things like 'figuring out how to put a bottom in it' before you start, that's the bit that's going to hold all the weight?!? It should be sitting ON the cross planks so that could be tricky to figure out.

Looks good I think though!

But $500, ouch!

Still if it lasts you a decade or more, it's much nicer to have something you've made yourself.