I think it's so hard to develop a trade simulation with the value they put on players specifically the Dbacks. I don't understand why Alek Thomas is valued at 9+ and Merrill Kelly is at 4ish. To me SP that are real solid are worth more IMO. I get that it's the final year of his deal but these values truly don't make sense.

You sort of answered your own question there, but here's the overview: https://www.baseballtradevalues.com/valuing-major-leaguer We have a 93% accuracy rate with our model over 6+ years, so the basis for the trade values has been established. It's surplus value -- the amount of "field value" a player is worth (think what they'd be worth if they were a free agent) minus their salary (since the acquiring team in a trade has to also pay the player). This is all calculated over each player's span of control. Kelly only has two months of control post-deadline, whereas a player with more years of control will typically have more.