That's a great thing to think about. IMHO, it's about worth and intent - as with any. And as with any software development, it's all relative. For me - personally - coding the map was a way for me to practice leaflet, which I've always been interested in learning, and at the same time D3. I never really thought about or even expected the campaign reaching out to me. The original map which is in bernie2016events.org used to take events from meetup.com and facebook.com, which I have scraped and manually curated. The campaign's open API for the events happened later.
So for me, the map was a practice exercise, which is essentially like a more convoluted Hello World. The value was perceived by others, and the campaign. The value for me was, "Ok, there's cluttered events all around the wild, I'd like to make sense of it and help out while I practice D3 and Leaflet."
The value as perceived by others was beyond me, and I was really just happy that it had bigger value that I originally intended.
This is different with foreign governments contributing online assets or money to the campaign, because the intent is different, and the worth is different. The intent is influence/leverage, and worth is tools/dollars. And as you have predicated below as well, corporate money is very different if you look deeper, compared to an individual who's just practicing.