20% ECM isn't bad for 60 points, 2x 6AP clusters is bad for 30 points. You could double the loadout for 60 points (Jag will carry up to six BL.775s) and I still wouldn't take it in Commonwealth. That's how useless cluster bombers are.
In my opinion they have their uses, but that's not the whole story. Compare the F-111C to the Il-102 - the latter still has 10% ECM and is much slower (albeit with a very good turn rate). I don't know how good the Gsh-23 is but I think it would be better if it counted as a flare or chaff gun. The trade off between payload and survivability is a difficult one, but I think there are some planes that are too likely to take a hit. I would like to see the Tornado get a larger payload but it could also do with more speed, it's faster than most planes at low level. I have other ideas but I can't say much about pricing because I just don't know.
The ratio for ground units excludes max range, optics and armour. There have been times when range was increased or decreased with no change in price. It's possible that some are discretionary, depending on the standard(s). Optics mostly coincides with range although there are some exceptions, armour seems to scale fairly evenly and speed/fuel values are similar. You can see where they've used modifiers to balance things like range and damage, for example the T-80 had poor optics and the size was set as large rather than medium, as per Abrams etc.
TL/DR: There's a logic to pricing but it's not that precise.