Correct, but the lowest discount price was $30, and the game also has two more expensive editions for $60 and $90. You're also right that we can't consider every owned copy as sold, but steamspy is quite accurate, something that's been confirmed by several developers.
One thing we have to consider is that many of these were backers already and part of the game's budget, so that's 77,000 people who didn't buy the game afterwards. The Witcher 2 had 80% of its copies sold on Steam and The Witcher 3 had about 45% (more copies sold on GOG), but that's the absolute best case scenario for a game on GOG, as it's the developer's own store, the game gets a few extras, loyal fanbase wants to support them, etc.
I'd guess at least 80% activated their copies on Steam, so that's ~62.000 copies out of the equation. That equals $12,500,000 in revenue for Obsidian/Paradox, but that's assuming all copies were standard editions, so if anything, they made much more than that.
Best case scenario, let's assume 20% of the copies were deluxe editions (I'm guessing here, I've seen some similar numbers for physical limited editions, but not digital only), 15% for the Champion Edition and 5% for the Royal one. That would put it at $13,794,684.
On a different note, I'm not sure, but it does seem to me that PoE was funded by Kickstarter/Paypal alone, unlike other crowdfunded RPGs. Wasteland 2 had its budget doubled (3 to 6 million) with InXile's own money, but I couldn't find anything to suggest it was the case here.