Exactly.

For close in flights, I frequently see Economy close to selling out with only a couple full fare refundable Y fares available where as Prem Econ often still has the cheapest E fare buckets available. Thus PremEcon is cheaper than Econ... if you must travel on that specific flight and don't need the increased flexibility rules of a higher fare class, then it's a no brainer to buy PremEcon for cheaper than Econ.

If buying tickets far in advance cheapest PremEcon fares tends to have a big 50-70% price premium over the cheapest Econ fares though.