ebay and hipstamp give
some idea of what's currently happening (keeping in mind that unless you search for "sold" listings, you're only seeing what someone is
asking, which might have little bearing on reality). Nevertheless...
If you go to hipstamp and search for "Newfoundland 49" you'll get dozens of listings, from a couple dollars to hundreds of dollars. You'll see that there are some pretty inexpensive stamps that, to be honest, have more eye appeal than the example posted above. And, some have less.
If the book you found is Scott or Unitrade, take a bit of time and read the introduction section. Either one is
well worth your time.