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So let's allow A to represent the cost of producing the comic.
Let's let B represent the amount you're selling each comic for.
So, C will be the amount of profit made.
So:
B - A = C
If C is zero you've broken even, if C is less than zero, you've spent more money than you've made, and if C is above zero you've turned a profit.
So C being above zero would be a "success."
While that is a great summary of reaching a profit, breaking even or a small amount of profit is rarely considered a success especially if that is the criteria for sequels/continuations/similar products.
So a one off single comic that has zero expectations might be a success if it makes a small profit, but as a test to see if it should become a series a significant amount of profit would be needed.
It was mostly sarcasm (a la Fight Club recall/no recall equation), but thank you for the compliment and the more detailed writeup of what actually matters.
So with adjustment:
If the goal is to make a living wring a serial comic, success would be having C>=A so you can afford to keep making and publishing more comics.