really comparable. They compared paying down a mortgage at 3.5% (a passive, risk free investment) to actively investing and managing a real estate investment, with significant leverage. In simpler terms, you took money and invested sweat and debt and made money. You needed the $11K to do it, but all of these examples compare a passive investment to the results of these active projects.
That would be like me saying I made a $11K investment and worked six months and made $200K in my job, sold my investment for 11K, with total proceeds being $211K or a 19X return on investment.
Apples to Oranges.
That being said, combined with your skill set, I agree with your action taken, because the synergy created is much more significant than what you would earn in a passive investment, whether it be a mortgage paydown, or almost any other passive investment.
Not advocating anything, but I wish I had your skill set. I was a landlord once. It wasn't pretty...and I am not very good with hammer and nails either...