This company realized a .io domain wouldn’t cut it.

Snappa acquired Snappa.com for $40,000.
Snappa upgraded from Snappa.io to Snappa.com for $40,000. You can read the full story here, but here are the highlights:
Inspired by Sumo.com: the founders were inspired by Noah Kagan’s podcast about why he paid $1.5 million for Sumo.com.
Also inspired by Teamwork.com: they also saw a presentation about the growth of TeamworkPM.net when it bought Teamwork.com.
People were confused by the .io domain: some customers emailed asking why their site was down because they went to snappa.com instead of snappa.io.
Legitimacy: they wanted to own the .com to show they were legit.
They could pay over time: Like Sumo.com, they agreed to pay some upfront ($20k) and the rest over time.
The blog post outlines the negotiations as well. It’s quite interesting.