I think that analysis is also short sited. Yes, they where upside down on their marginal costs right now, but that's because they went the minimal engineering

I think that analysis is also short sited. Yes, they where upside down on their marginal costs right now, but that's because they went the minimal engineering effort way and used AWS to get things started. By raising a large(r) round they, presumably, could have hired an infrastructure engineer or three and moved away from the higher costs of amazon. If they had gone that route from the beginning they would have had to sacrifice some other part of their business because they would have had to hire for that role...and that could have been more expensive than just paying Amazon to get things off the ground. So yes, they could have saved on operations, but either at the expense of product or at the cost of another engineer or two...thus increasing depth of the human capital sinkhole.