You missed what I'm saying. I said that scouting will determine who wins and loses deals ultimately, especially if surplus value is roughly even in the deal. My point is that because surplus value is basically the way value (or whatever you want to call it) is determined on the market right now, you are making a bad deal if you're giving up more in surplus value than you're getting back. Not because you are definitely getting a worse player, but because you could either get more back or give up less.
Let's say for argument's sake there is a corner outfield bat we really like, and he has a certain surplus value according to the market. And let's say that we are ok giving up Teheran to get that outfielder, but Teheran actually has more surplus value according to the market. If we make that deal straight up, it doesn't mean we will 'lose' the deal in the sense that we will definitely end up worse off by having made that trade. But it does mean we will be worse off than we could have otherwise been by making a different deal. We could have either gotten the outfielder plus more, or we could have given up less than Teheran to make the surplus value equivalent.
Again, surplus value doesn't necessarily indicate you made your team worse. It just means you didn't negotiate well and likely could have made an even better deal.