On the stipulations that are presented for the comparison, essentially the $2,000, $2,700 and $5,800 ticket prices for the three classes of service offered, I wholeheartedly agree with kiwibigdave's assessment and conclusion.

However, as Kiwi Flyer points out, the price difference especially between E and PE could easily, and in a realistic scenario, be a lot more. If you're travelling for a holiday and you book your ticket well in advance, as I think is common for a f.ex. US to NZ vacation, you are most likely comparing a very discounted E to a "standard" PE fare.

Spot check on airnz.com for a 2 week trip on random dates in late Feb07, LAX-AKL return:
E: ~USD1,200
PE: ~USD 2,800
(BP: ~USD 6,300)

Out of my own pocket... I'm not sure the extras in PE are worth USD1,600 in this scenario.

Now, if you're a business traveller restriced to economy travel but you're travelling on a much shorter notice with, probably, very limited access to cheap Y fares, kiwibigdave's comparison is probably more relevant and the upgrade to PE a better deal.