Re: Come on guys
I understand that over-promising is a thing, but if that over promise is tied into getting someone to do a thing now in expectation of a thing in the future, then it's lying and manipulation. Or sales :)
If I say I'll paint your house for a tenner, and you agree (and turn down other offers to do it), then I turn up and say "oh, I meant a grand" would you shrug and say "oh well" and give me the cash? Would you fuck. Cost is a major factor for most decisions, and doubling it indicates that the initial price was waaay off. If you want to avoid damaging the brand, being upfront that you've fucked the numbers and things are going to be more pricey (but quality will be good) might have been a better tactic.
Manufacturing is tricky as you say, even experienced groups can make huge errors in planning and operating that lead to large (and possibly prohibitive) costs. That goes doubly for new products, and small (sub 100k for widgets, sub 10 for big things) production runs. So if you're going to promise a product (a la Kickstarter) then you should have a plan for cost over-runs, delays, and other people being full of "idealistic views*" that result in them promising things they can't deliver.
Crowdfunding (and unicorns) seem to have this as a common issue. Someone thinks idea X will be awesome, despite X being somewhere between difficult and impossible. Person then assumes that X can be done right first time both in design and production, and doesn't bother to build a prototype. After getting funding for X, it turns out to be waaaay harder than planned, so company folds, after taking the cash.
* There's a cultural factor too, some places will simply not say "no" or "that's not possible" even when you are clearly asking for the moon on a stick, yesterday, whilst being showered in unicorn piss.