How to calculate pricing if you want to run Life time deal campaign?

For lifetime deal (LTD) pricing, it helps to consider a few angles. First, assess your long-term support and hosting costs per user, then factor in potential feature updates they’ll get access to over time. You’ll want to balance an appealing LTD price with the cost of covering these ongoing expenses. One strategy is to analyze your break-even point—estimate the number of LTD buyers you’d need to cover your core costs over the deal’s lifetime. Also, consider offering tiered LTD pricing based on feature sets. That way, you can cater to different customer segments while ensuring that your highest-value users contribute proportionally more. Good luck with the campaign!

I ran a calculation based on a similar assumption as @kamuidev mentions in this thread and offered a LifeTime Deal (to my own list) that was equivalent in price to 3 years' subscription, but with ~10 years worth of non-expiring credits and many other perks.

It was mildly successful (in terms of number of sales) but wildly successful in terms of generated cash.

Platforms like AppSumo seem more targeted at "getting a big influx of new users" (who pay you almost nothing) and are only interesting, IMO, if you aim to get reviews/social proof that you can't get with your normal marketing efforts.

But doing a LTD by yourself to get low numbers of low-paying users makes no sense. I think it's either: big numbers (of users), or big cash intake, otherwise it makes no sense.

Stripe has a good guide for this, look up "the saas business model stripe" and go to the "The fundamental equation of SaaS" section.
TL;DR: get the average amount of periods (months) a user subscribes for, multiply by price, and you get lifetime revenue. Adjust LTD pricing based on that.