I thought the article just cited did a reasonable job of describing the tradeoffs.
How compelling winglets are may vary by route.
Some of the benefits may matter a lot on some, not at all on others.
On some routes 1000 pounds of additional cargo may be more lucrative than a small fuel savings. On others the fuel savings may be large.
Way to hold your own, Mount Athos. Duly impressed. (Tips hat)
Well, now, I’m confused again. Don’t winglets give additional lift? Wouldn’t additional lift translate into additional payload? Wouldn’t additional payload translate into additional revenue?