Carl and Jerry have the same plan (spoilers obviously)
Jerry's grand plan was to deliver the random of $1 million personally, take $920,000 for himself and then give $80,000 to the kidnappers who would be none the wiser.
Once Carl murders Wade and realizes the ransom wasn't $80,000 but $1 million, his plan is to take the $80,000 to split with Gaear, keep the $920,000 for himself and Gaear would be none the wiser.
I believe the reason Jerry showed up to the meeting between Carl and Wade is that after the handoff he probably thought he could convince Carl to split the $1 million 50:50.