That was Lan’s initial calculation. When you challenged it, they agreed with you and revised their next estimate upward. No one else has suggested it only sold 30k. But I disagree with you that we can be sure the series sold 300k or more, on the basis of my own sales experience. Review to sales ratios vary so wildly that I just don’t think we can place as much confidence in them as you are.
It’s possible you’re right about it all. But if so, Sera’s series has earned half as much as virtually the entire CoG library over 10 years ($2m in royalties, per the reminder above). That kind of wild outlier seems unlikely to me. I don’t mean to insult you, just to disagree with you.
Like I said above, after discounts, mine has earned me $1.15 per sale in royalties. Wayhaven 2 and 3 will have earned more than that because of their higher price point. Maybe WH1 will have too, despite the similarity to XoR.
Edit: Glancing back at the bestseller list, if Wayhaven has turned over a million, then @JimD is low-key Scrooge McDucking it over in the shadows. 
Edit 2: And having just downloaded the HG omnibus, I note that Safe Haven, the #1 HG bestseller, has half the ratings (almost 10k) of the two main Wayhaven games (about 20k each). That’s a useful reminder that sales numbers aren’t proportionate to omnibus ratings in any but the roughest sense. I’m happy to agree with you that Sera’s sales comfortably exceed her ratings, Sam, but as soon as you want to put a “5x” on it you go beyond what I think we can know.
Finally, even taking 5x 48,000 – which is the total omnibus ratings I see on all three WH books to date – doesn’t get us all that close to a million sales, or necessarily even to $1m in CoG revenue. Doubling WH1’s rating numbers to account for it coming out pre-omnibus adds 100k sales to your estimate; given the much more modest numbers people have shared for other successes (FH as well as XoR) I’d be surprised if that were accurate.