What favour is suitable in return for running a costly software?
There are probably two important parameters for this question: (1) how close are you to the other party?, and (2) how long will it take the other party?


If you are good friends with the other party, and it will only take a few minutes - probably no favor is needed, as long as you don't need this service all the time.
If you are good friends with the other party, and it will take hours or days to do - in this case I would consider whether it is possible to set up the project in a way that co-authorship for the other party is legitimate. Yes, just running predefined scripts or doing some analyses that you have clearly laid out may not be enough to warrant co-authorship, but typically it's not a given that this is the only thing they do. Just get in touch with them early on in the project, and collaborate.
If you don't know the other party well or at all - in this case, it seems unlikely that you will be able to convince them to run your software just as a favor, even if it does not objectively take much time. Your best bet is to get to know them better, and see if you can start a collaboration that will include, as part of the collaborative work, that they run the costly software for you.


(of course, all of this assumes that the other party actually already has the software and using it for your purposes will not incur significant additional costs)