the iPad 9 offers great value, but the issue with value is that it depends on priorities so it's kind of subjective.
For instance for me the most important things in an iPad are: speakers, RAM, size and keyboard support. And to a lesser extent USB C and pencil 2 support.
Instead I don't care about screen quality (modern iPads are all good enough for me, including the entry level, I barely care about promotion and don't care at all about mini-led) and CPU speed (anything above A12 is plenty fast).
Size is easy for me, I want them all (mini, mid, large)
Speakers means that, other than the mini, I don't get anything that does not have quad speakers.
Having said that in my opinion:
- the 9th gen iPad has great value for money (if I could only afford that, I'll still be happy provided I have airpods to replace speakers)
- the air 4 has the worst value of all (only 1GB more RAM make little difference, same storage, speed doesn't matter, and it costs double the price)
- mini 6 has meh value (same storage, same RAM as the air, no keyboard support, at $100 less than the air and $200 more than the iPad 9). Personally for me not worth the upgrade from a mini 5 (but if I had no mini 5 I would still consider it)
- the 11 pro has very good value, even at its price (double the RAM, the storage, the speakers of the air, smaller bezels, magic keyboard support, plus a few more bonuses)
- the 12.9 is not a great value IMO since I don't care about mini-led (I'd go with a refurbished older model, and that's what I did)
I know that for some people the display (laminated, promotion, mini-led) is the most important thing, some don't care about speakers or RAM, because they don't use the iPad for the same things, so they'll have totally different priorities and different view of value....