I use $2/lb as a baseline. In my area it works for both meats, and produce.
Basically,
If it costs $2/lb I'm ok buying it.
If it's <$2/lb, I stock up. If it
If it's >$2/lb, I don't buy it unless I need a small amount for a particular recipe.
In practice, say asparegus is on sale at $4/lb from $6/lb. That's great, but is it worth $4 vs the $2 I could spend on brocoli? So I eat brocoli this week.
Over time, you'll know what's typically more or less, because you'll know what you eat often, and what you never eat. The day you show up, and see the asparegus is finally at $2/lb, that's the week / month, you eat asparegus to your heart's content.
I apply the same to meat. I look for $2/lb boneless. Doesn't matter if it's chicken, ground beef, sausage, bacon, whatever.
As a side note, onions, green beans, and squash crush my $2 threshold all summer long. I tend to buy all 3 on every trip to the store.