Surely he didn’t ask to be paid in dice? How many Livre, Fifths, Thrones is he asking for?
That aside, I’m with your player–I’ve even made a similar argument to my current GM: My GM asked if I had any Cash Dice to give a thug as a bribe. I told him, “We buy stuff by testing Resources; not by generating cash to trade.” Swapping Cash-gen Tests can be a seductive convenience, but it can also be a red herring–even if the Task in question is giving an NPC a bunch of cash! Cash Dice are extra dice used for Resources Tests. The degree to which cash is helpful to acquiring a good or service is variable–which is why the mechanic is so unstable. 4D of Cash can be enough money to hire a bodyguard or only enough to buy food for a day or not even that–or (in the right hands) buy a castle! Further, Obstacles don’t equal money, they equal difficulty, and they don’t even necessarily equal “realistic” difficulty. Throwing around cash on a day to day basis is super easy. Having cash when you need it, like, “I need to leverage every asset I can for this buy” need it can be quite challenging. It’s an Ob 8 Test to generate 4D of Cash. It’s aslo an Ob 8 Test to buy a small cargo ship. That doesn’t make any kind of sense if you assume that Ob = Money. Even if we imagined that Cash was super difficult to obtain and so came with a double obstacle penalty to generate, 8D is not enough to make buying the ship Routine. It seems like having the Graverobber ask for Cash Dice is putting the mechanical cart before the narrative horse and artefacting the system pretty hard. That brings it back to my earlier question: How much money is he asking for? Cash Dice isn’t money. This NPC isn’t playing the game; Cash Dice isn’t a thing for him.
If we were assuming he were playing the game, though, why does he want cash? I’d take a 2D Fund over 4D Cash (almost) any day, and a 3D Fund is still easier to create than 4D Cash. Buy me a rich-folks’ cemetery that I can rob nightly for an enduring +3D to my Resources. If he’s looking at the rulebook and shopping, he could have your player finance his lifestyle and live like a Count for 10 Maintenance cycles at Ob 8 (Base 7 + Buying in Bulk) or like a Baron for 100 cycles! Ten or so years of fine living or the ability to semi-reliably buy food for a day twice? Easy choice! He mentioned hiring extra muscle. 4D Cash ain’t gonna cut it (without Help, Artha, Resources, etc.) Hiring a bodyguard is an Ob 4 test, +1 for buying in bulk. If I’m playing the Graverobber, and I’m honestly trying to help my buddy, it doesn’t make sense for me to demand Money Bags tax his Resources to give me Cash so I can go fail a test on his behalf. Especially when he’d have an easier time making that test himself (probably). If the graverobber is asking for money to finance the expedition, he should really just cut out the middle man and say, “I’ll go. Here’s a list of stuff I need. I know where to get it; I just need the dosh.” Then, you set a Resources Obstacle.
That’s my first bit of advice. And, Situation willing, let Money Bags haggle, score a deal, and generate Cash for themselves to help with the roll. I’m not saying harrowing expeditions for lost artifacts are cheap. If the graverobber is saying, “Sure. I’ll dig up Blackrazor on Monster Island in the Land of the Dead. Gimme a million bucks,” that sounds fair to me!
If he is really willing to go, my first instinct was to say to the player, “He’s your Relationship; sure he’ll go! If you wanna send 5 resource points on a suicide mission without providing him the means to have any hope of success, he’s 100% on-board! (We’ll check in with him in a few sessions when he’ll have never been heard from again.)”
Other than that my criticism is that this expedition sounds like a heckin’ fun adventure! It seems a waste to have it occur off-screen!
… And so my ultimate advice is to not let the adventure happen off-screen! Tell the player, “You don’t have to give him anything; he’s packin’ his bags! But feel free to give him as much as you want! Give him a letter of introduction (Help with Resources); back it up with a letter of credit (Fund). Buy him arms and armor. Book his passage on a junk and shell-out for a spade with a balance die. And make sure his character sheet is up-to-date; you’ll need it. Everyone else, burn up new characters in Graverobber’s circles. Next week Money Bags is taking his relationship for a spin, and you’re all going with him!” If it’s not the kind of thing you’d run, ask someone else to run it and burn up a character yourself!
Also, what are the player’s Beliefs?