The Liebman book is solid. He's very analytical in his approach and meticulous with detail. No nonsense. Takes a lot of what he learned from Joe Allard and put it in a book.
That said, I've always been partial to the old standby "Top Tones for Saxophone" by Sigurd Rascher. And I think it may come in at under US$10.
And, actually, IMO, the BEST way to develop a personal saxophone sound, ironically enough, is through transcribing. Learn BALLADS (melody only) by ear from recordings. Really pay attention to the nuances of tone and try to emulate it on your own. You'll NEVER sound just like the record. This process actually helps you uncover YOUR sound. And the more sax players you "copy" in this way, the more dimensions of YOUR sound you'll reveal.
I have one more approach to developing personal tone/sound, but I'll have to save it for another post, if you're interested in hearing about it.
best regards from Pennsylvania!
~ Rick