Only read two but both were great:
Just Gus by McCall Hoyle: companion novel to Stella, this one featuring the Great Pyrenees from that book, injured while guarding the sheep, recuperating off the farm with relatives and finding new purpose as an emotional support dog to a boy with anxiety.
Falling Out of Time by Margaret Peterson Haddix: the over-25-years-in-the-making sequel to everyone’s favorite r/whatsthatbook request, Running Out of Time
I’ve gone up to $50 for scarce, out of print books I want to make sure I have lifelong access to.
For small-press-published books I’m unlikely to find secondhand for less than half the publisher’s price if at all, up to $20.
For the average book I REALLY want, up to $10 if I’ve been searching secondhand sales & shops for a couple of years and haven’t seen it yet.
For most books though? (including ebooks) It’s a hard cut-off at $3. Maybe $5 if it’s brand-new.