Actually we had a pretty detailed financial model for how we expected to get to profitability! We currently have ~1,200 subscribers, and about half are paying us $1.99/mo (our old price point) and the other half is paying $3.99/mo. Our growth model is based on people sharing our content, and so we can predict pretty well how many new customers we'll get every time we post something new. With a $15k monthly content budget (a couple writers, network of freelance designers) we were pretty sure we'd be able to bend the growth curve to the point where we'd reach profitability (~15k subscribers) in about 10 months, assuming modest improvements in conversion rates and share rates (we'd obviously be doing a ton of experiments to move these numbers).
At the end of the day, investors weren't convinced, so you certainly have a point! There may have been something seriously wrong with the plan. But I challenge your assertion that we'd need "big growth just to survive". Yeah we'd need pretty good growth, for sure. But not "unrealistic, crazy unlikely" growth.
And on the upside, once we got there, all growth would be pretty much pure margins after that! We don't think we'd need to dramatically increase our investment in content.
Basically, it might not be as dumb as it seems.