@SpeakingToHe,
Even if used book stores are going out in
your area (there are several HUGE ones in my area, and nowhere near to going out of business), there is, you know,
Amazon.
Where backlist books often sell for a penny plus shipping.

And where "searching" takes about 30 seconds.
If shipping is $4 a book, then it stands to reason that $4-5 would be a sweet spot for a backlist eBook.