Money represents effort and resources, so while it is worded flippant it is a valid point that we shouldn't assume interplanetary flight is just a weekend away for aliens.
We don't know the conditions on that theoretical alien world. They could be post-scarcity, or alternatively, they could be threatened to the extent that no cost is too high.
He is saying there is no reason to assume they have reached that point just to explain something that is most likely a misunderstanding of something mundane.