That's a big factor. Even "slight traffic" can yield significant value IF the leads generated by the domain are very high value.
You're somewhat hunting my smell alone, which for human's is a bit of a challenge.
Sniff out this: Visit BuyDomains.com and see if they are selling any "close variant" and at what price. See if your version has been registered in any other gTLD or ccTLD and who registered it. See if there are reports of near variant sales. Search the word/domain in G and see how many exact matches your get and how they are deployed.
You are somewhat in the "made up domain" world, a place where anything goes. Most of the time people just look for other options, but sometimes it's a case of "just gotta have it".
An initial offer can be construed as a percentage of what someone might pay. You can make any assumption you want. One-half may be a safe assumption.
The worst that will happen is that your buyer will take a hike and you'll never receive another offer . . . but at least you'll have a decent war story to tell at some future conference. ;) (Maybe you'll get a free "sympathy beer" if you cry a little when you tell the tale.)