Whatever amount that they would need to eat in Castellanos contract to unload him.
Gonna be far more than that.
Castellanos is gonna cost 60 million. Trout still has 245 million left. Figure the Phillies would want the Angels to at least eat the difference over Castellanos contract, plus equivalent amount through the rest. Call it 100 million even for the Phillies to cough up Mick Abel and maybe another prospect (Aidan Miller? Carlos De La Cruz?) Eating 60 million got the Mets Luisangel Acuna, currently the numner 38 prospect on MLB Pipeline. Mayne for a 100+ million, the Angels would expect Painter, particularly if they're taking on Castellanos.
OTOH, if it's just taking Castellanos, they'd probably get a prospect in the 18-25 range on the Phillies top 30 chart.