A dollar here, a dollar there, there is a dollar everywhere.

It is always “come for one and stay for the other” that helps an organisation create a strong business model. 

Apple: Come for iPhone, enjoy for the superior camera experience, pay for iCloud storage (seriously still 5GB free?, not allowing WhatsApp backup on iPhones on the other cloud?) and stay for a unified experience. 

Microsoft: Come for Word, Excel, Powerpoint, stay for convenience and pay for productivity and if you are SMB, LE then pay for collaboration and productivity. 

Google: B2C Come for free and innovative mail, stay for extra storage once 15GB of not just mail storage (or photos, mail, drive) gets blown over (++ exporting mail from gmail is a slow enduring pain that every happy human should face once in life to understand what misery is), 

Common thread is find a business vertical that would allow you to get a market dominance and then create a digital product value added chain to milk the user base.

Dropbox with 2TB storage is the pariah here. Dropbox Paper failed as iCloud notes copied the features. OCR on the notes and drive is also a standard offering. Adobe Document cloud could eat the competitor alive for OCR or for that matter any advanced file manipulation. I recommend bundling the Dropbox storage through the image sharing, collaboration, productivity web services to create a stable revenue stream for storage. Collaborating with the external portable hard disk drives for free cloud storage entitlements would also help.