"Luxury" upgrades is just a nice way of saying player that is killing my season slightly less than a "real" upgrade...
If you're using the extra trades to fix problems while others are using them to upgrade, you're falling behind.
I don't even hate the Serong pick, there can certainly be a case made for him going 110+ and at his price, assuming M8 cutoff is around 115, that would absolutely work as a pick but there's a pretty wide range between his starting price and that point that really doesn't work as a pick. You've essentially given up a shot at a premium on other lines for a midprice pick that doesn't make enough cash.
Serong has to be picked for keeper potential, you have to genuinely believe that's possible. If you do, go for it, if you don't there's just better ways to spend that money.
I think a lot of people are getting fixated on extra trades without thinking about the reason we have them, COVID is almost certainly going to cause some issues, until our governments get with the times on it and start to remove this case/isolate stupidity it's going to be impossible to avoid it hitting SC really hard and not many of the governments, especially VIC and WA where a sizeable amount of the AFL is based, are interested in doing that. There's a very real chance that despite the 5 extra trades we really have 5 trades less this season to actually use, especially if your team is lacking depth.