They are not going to QO Arrieta. And he's also not going to fetch much of anything in a trade. Think along the lines of the return for Utley or Chooch. Maybe you are lucky and get a Nick Pivetta like we did for Pap.
More likely if they are out of it they would happily give him up for nothing to lose the month's salary, which would exceed the value of any prospect return you'd have to buy by continuing to pay it for someone else.
With teams limited to their 60-man pool and valuing prospects more than ever ahead of another year (two years, really) of economic uncertainty, it just won't be anything to worry about.
JT and Didi could be a different story. There you'd be weighing their value to the team against the value of the QO against the potential to re-sign them.
If the rotation is going well on August 31 you're not gonna want to change it. And if it's going badly it's not going to matter. You dump Arrieta and suddenly Cole Irvin is pitching in those doubleheaders.
I've had exactly the opposite thought about Price - granted it is very early but it seems like our bullpen is exactly as talented as it was last year (just different names) and no better, i.e. talent and health matter a lot more than coaching. Same with the rotation really, it's better because we have Wheeler and Arrieta is healthy, Eflin and Velasqez seem about the same (yes, last year's coach didn't handle Eflin well, but then they sorted it out).