If the result of those thousands of hours is worth <= 10000 by some valuation method which makes sense to me.
More nuanced answer: I have a project that I've been plugging away at for years now. It may never pay for itself if I value my time at the same rate that I charge it out to others, but in that time it's improved the quality and speed of my other outputs significantly.
In that regard it's probably already paid for itself, but I wouldn't sell it because it continues to be valuable to me both in that regard and as a creative outlet.
If it were a throw stuff at the wall and see what sticks saas I'd have no problem selling it for a reasonable valuation of future earnings.