I looked today to purchase Core Tunnel. I'm lazy. It works great. But frankly - $10 / year is WAY too much money for the utility I derive out of it.
In about 10 minutes, I can whip up BASH script that does exactly what core tunnel does. Is it sexy? No. Is it neatly docked in my Mac? No.
I was prepared to pay $10 for a perpetual license. And would have happily done so. But i'm not interested in paying $10 on an ongoing basis.
Please accept my input merely as "one users view". I'm sure there must be people willing to pay that year after year. I'm simply not.
Good luck - I do love the product, and I will leave a 5 star review for the free version.