You are misunderstanding. The Nebula people were previously using the Whitney typeface. The organization that produced/sells Whitney changed ownership and the licensing became prohibitively expensive overnight.
They wanted something that could be a drop-in replacement for Whitney with the same letter sizes and spacing, so that they could put it into all of their products without needing any other redesign.
They couldn't find anything like that available off the shelf, and fonts they found that were close to Whitney in appearance were still also somewhat expensive, so their alternative was to take Source Sans, which has a free license, and make some quite significant but semi-automated modifications to it.
Making changes to just the typeface was presumably cheaper than making changes to all of their other designs.
Perhaps I'm your typical HNer like the GP comment and the topmost comment, but I don't see an issue with changing the style of the font entirely. Sure, it may be jarring to customers, but it's a short term pain for almost zero cost.
There's no inherent issue with it. It just requires doing a bunch of additional design work, which is not free.
Is it more expensive that designing an entirely new font?
That's why they didn't design an entirely new font. Instead they made semi-automated modifications to a free font, and then tweaked a few specific characters afterwards.
The result is not as good as what they had before, and not as good as it would have been if they hired a professional to design a new font from scratch, but it was cheap and solved their problem.
They took something workable and Arial-ised it. And now they're using a bland, mediocre font.
Fonts are weird voodoo. Good and bad choices can both make a measurable difference to ROI.
So I'm not convinced this is going to be the profit booster they hope.