So they must have some form of business model, right? All I can see on their website is that everything is for free, even their API which can be used for free without any limits or restrictions. And given the already huge Imgix costs, abusing or over-using their API to request and resize images would directly increase their overall costs. According to Crunchbase (https://www.crunchbase.com/organization/unsplash#section-fun...) they raised $10m last year, but they must be churning through $3m+ per year on staffing and hosting costs.
I use and love the service but I can't see how it can last for more than a few more years.