I just read your post using your link. You are right if you need to pass 25% curation reward when there is really an upvote for your post from one of your readers within 30 min. The method I mentioned only works when you do not receive any upvotes after 30 min since curation reward based on my understanding only needs to pay within the first 30 min timeframe if I am not wrong. My assumption is also not just 30% profit from buying upvotes. It only works when you are able to buy upvotes that offer 130% of profit. Those that requires bidding does not work as unpredictable as well.

I am presently using steemlike which is not by bidding.

Hopefully it stays like this but upvote bots can be unpredictable like your experience. This post is just some thoughts that I have and I added a disclaimer so that I don't misled anyone. Thanks for posting this comment.

For steemlike, we use this link to monitor our purchase but it takes many hours before an upvote
https://koinbot.org/#/steem/like

You can also visit their site to find out more about it.
https://steemit.com/@steemlike

Thanks for sharing and I hope I did not mislead anyone from my thoughts!