Hey Ryan,
Thanks so much for your detailed analysis, this confirms the gameplan we had to remove thousands of links to our site. We ended up contacting about 800 webmasters who owned ~2,500 domains total with spammy links to our domains, and we had about a 6.5% response rate.
About 42 site owners responded and removed their links easily. Then there were about 10 who responded that they would take down the links for a fee. We've paid 8 website owners for a total of about $135 but there are three more that own a ton of domains and they want another $410 total for about 75 links.
We are trying not to spend that much on link removal, do you think if we document this and send it to Google they will understand the high cost that we don't want to pay, or will they just tell us that we have to pay this off if we want the manual penalty removed?