Frankly, I'd say if you can't compete, then don't try to.
Of course, I ordered my 24g from aquariumplants.com so I enjoyed the good prices. But frankly, the $250 price for a 24g aquarium is already pretty high when you compare it to what you could get for that money in a non-nanocube. Of course, I've heard of people paying like $350 for them which is totally crazy.
The aquariumplants.com prices were just plain reasonable in my opinion (and hence why I bought them at the sale price without much debate).
Now the 6g seems WAY too pricey, since it costs much as I've seen 12g ones in the LFS for.