Xander is homegrown talent and we gave up some younger talent for Sale in a trade. They are both getting a raise. Not quite similar to DD signing say Price in an open market.
You build teams in 3 different ways.
1) Homegrown talent....you should know, Yankees have done it in recent years. (Xander, Betts, JBJ, Dustin, Beni, Devers, etc)
2) Trade....basically two teams trading players a) surplus of talent at one position or switching out major league ready talent for talent further out in the minors. (Sale, E Rod, Porcello, Eovaldi, Pearce)
3) Free agents (Price, JD)
I think DD has used all three modes to enhance the roster. Perception was Yankees used method 3) when the old man was running the team.
I think I saw an article in Fangraph detailing the composition each roster.