One small consolation about the killer's parents going on the lam is that when they are found,

[Irish_Dem]

25. I like this idea, but yes the reward is the problem.

And I don't think this couple is smart enough to pull off this plan.
They would have to blend in as transient meth heads.
And yes the meth heads would sell them out in 24 hours if a reward was on offer.

Also this couple only has $4K, won't last long, and once the money is gone, the methies will toss them out.

They could hide in some out buildings, barns, etc for free. But I don't think this couple could manage it for long.
And once is starts snowing, residents, mail delivery, etc will notice footprints in the snow where there should not be footprints.

I don't know, maybe stealing a car, doing a complete appearance change and going south is a better option.
Head for Mexico?