As I've said before, if you trade a superstar, you are not going to get comparable value, period, plain and simple. If you get a package of prospects and one or two them turn out to be productive MLer's, you've probably done alright, all things considered.
If there's an outlier to that rule it's probably the 1998-99 Ken Griffey, Jr. trade which ended up benefiting the Mariners more than the Reds. The Mariners got 18.7 WAR out of the deal while the Reds only got 12.4.
The Padres are certainly doing all they can to accomplish something during this current window of opportunity. Remember Manny Machado has his opt out after next season and many think his heart has always been in the Bronx. Soto will become a FA the year after that.