IRL examples: The Vietnam-Era A6E Intruder served with multiple upgrades until less than a Decade ago (1962-1997) as it did its job very well. The B-52 Stratofortress as well as the AH1 Cobra have been upgraded numerous times (IIRC the latest AH1 upgrade in service with the USMC is the AH-1Z Super Cobra), and are still on active & combat duty. IMHO the same applies to the Y-W: old but still gets the job done...with the right Upgrade Packages.
I believe that the Y-W may not be quite as good as the X-W in turn-and-burn furballs with light, fast, & maneuverable TIEs...but with good pilots & tactics that turn the fight to the Y's strengths could easily be a Bad Day for the Empire. Avoiding a turning fight & going for a nose-to-nose attrition battle would almost always go in the Bone Squad's favor. Think along the lines of the WW2 Pacific Theater, specifically the Mitsubishi A6M Zero vs. Grumman F6F Hellcat engagements for useful Y-W vs Tie tactics.
One of my Disney-Canon annoyances is the Rebels cartoon showing non-experimental versions (IRL these would not be XF nor YF models) of both A-Wing & B-Wing fighters on a fairly regular basis in an early Rebellion / mid Imperial Era timeframe. It'll be interesting how the Big D will explain them not appearing in the Premium-level Canon movies until ROTJ.
If the Rebellion had manufactured & deployed A- & B-wing designs in respectable numbers significantly before ROTJ why where there absolutely none present on neither Yavin 4 or Hoth?
Faux pas, Mister Mouse, serious faux pas...
It wasn't IIRC about price as it was Strategic Resource Allocation. Aluminum was a high-demand material. Both the DeHavilland Mosquito & P51 drop tanks were made mostly of wood products as it wasn't in such high demand to make everything else. The UK also had a lot of rather idle skilled cabinet and furniture makers along with a vast source of trees in Canada alone.
PS: I hate Otto von Logout for making composing well-reasoned posts of a middling length for this site a general Pain in the Sith...