So thanks to everyone, and the Kobo coupon being good on former-agency books, I've been busy filling in the holes to a few series. My threshold is still the same as it's been for the 10 years I've been e-reading. Check (my three) public libraries, and if I can't get it there, I'll pay up to $5-6. Maybe I should increase that due to inflation? Nah, don't need to thanks to this thread
This Kobo deal is dangerous... there are still several more I'm eyeing up, but I should probably wait for payday.