I bought Logic maybe 8-9 years ago, and get free upgrades.... If I had paid $5/mo it would already have cost me ~$280.00 more than I paid.
Even if I had to purchase an occasional update (assuming they were reasonably priced), I'd still be coming out ahead.
I hate "renting" software.
Oh yeah, my Logic for Mac is probably about that age too, but there's no choice to buy it outright on iPad sadly.