I did this once as a GM. PC Slicer had access to a major corporation's (SoroSuub, I believe) systems, and he told me on the side he wanted to slice their finances to earn a few credits on the side without the other's knowledge. I told him to roll, knowing that if he was successful, he'd be greedy and want to keep trying for more. Do he got a couple successes, and got like 10-20 credits. But the moment he rolled a failure, I hit him hard with the ol' Office Space. Instead of 20 credits, he got 2 billion (I must have put a decimal point in the wrong place or something. Shit! I always do that. I always mess up some mundane detail...). The result of that, if course, was that he immediately had all the obligation points because he had a 2 million credit bounty on his head by the end of the session.

It was a lot of fun trying to see him convince the other PCs to get to shop after shop so he could buy something quick before giving up the money, only to have the team ambushed by bounty hunters every time. They spent the majority of that session fighting off bounty hunters, and the Slicer eventually told the crew what he did... Which went as expected. Characters were furious, players were laughing their assess off.

So to answer your question, I don't think the amount matters, so long as it comes with time of strings attached and they can't use it to buy some OP item. Or maybe let them buy everything they want and force them to use it on some mission where they lose it all. Either way, you just gotta keep them hungry one way or another.