I have a number of instruments with lacquer, varnish and poly finishes, and have even applied lacquer and varnish finishes on new ("white") instruments in the past, but have never applied a poly finish... Lacquer and varnish are traditional of course, they have a nice feel against your skin and they are easier finishes to touch up, but they require multiple layers and polishing to achieve a consistent original glossy finish, they do evaporate and grow thin over the decades and they can have problems with constant wear, checking and cracking. Poly finishes don't require layers or polishing, they don't check and crack unless the wood underneath the finish is changing, they are projected to last nearly forever with normal playing wear, but they are hard to touch up (except perhaps spot touch-ups with layered cyanoacrylate) and they tend to get a sticky feel against the skin unless their gloss is muted by light sanding. Also worth consideration is that poly finishes are usually harder and often thicker than lacquer or varnish, which may be a tone or volume problem, or may be a problem when structural instrument repairs are called for.
With the same level of use, my 45 year old poly-finished instruments still shine like brand new, while my 45 year old lacquer and varnish instruments are starting to look thin and worn particularly in those areas that are constantly touched by hands and arms during normal playing. I think that a poly finish is what we are seeing with the OP's instrument. I have some 100-year old playing-quality instruments that I really wish were originally poly-finished; they are really in need of re-finishing, but changing those old original finishes is a hard decision to make. For a brand new instrument I'd probably wish for a lacquer or varnish finish but in 45 years I would probably wish it was poly.
When the finish materials are purchased in bulk as any factory would normally do, the only serious expense differences between any of these finishes is the labor of polishing and the cost of the equipment needed to do a quality finish with them. A poly finish of itself is not "cheap" except that it doesn't require layers or polishing, while lacquer and varnish finishes are more traditional and they do require multiple layers and extra polishing labor so as a result they can call for higher prices.