Okay. So. I haven't worked out Every class and spec, obviously, because that would be insane. But I checked a bunch. And so far, the ratio of effectiveness between prime stat and Worst secondary stat is no greater than 3/4.
(for fire mages Crit is actually Better than Int, so the gap between crit and worst is nearly 2/1, but that's a special case)
So. With a 3/4 ratio (worst case) and a feast for 150 primary stat, or 225 food (or crappy engineering Versa feast) as an alternate choice, the 225 WORST secondary stat works out to 168 primary equivalency.
For most specs it's better than that. That's just the worst I could find.
What's that mean?
Individual Food for YOUR spec > Any feast.
In fact - ANY individual food with 225 stat > Any feast.
ANY 225 buff > 150 feast.
How is that possible when (insert stat here) sucks for my spec?
Well mainly its that you have 23,000 prime stat, so 150 is nothing. It's about a 0.5% buff in fact. Food that's properly aligned to your spec isn't all THAT much better mind. More like a 1% buff. But good to know.
Also note that since I haven't checked every spec, there could be a spec out there for which prime stat beats out crappy secondary stats. To do so the ratio needs to be 0.66 or Lower. Or 150/225 = 2/3
Also don't trust Noxxic's values. Maybe they are accurate when weighted solely against other Noxxic values, but outside that they seem pretty made up.