I've found (for my games) when you say it's going to take a long time, its got to be something more like infrastructure, or something that requires a lot of hands involved. This is because a session in my games normally span a few hours, but rarely cover more than a day or two. Sometimes we pass time between sessions, but that's basically the only way to ever hit this particular requirement.
The cost in jingle requirement can be satisfied by just setting enough aside, meaning more time will be spent NOT working on the project, but rather preparing for it by doing other actions and putting more and more barter aside for it. This is fine if the project is something that can show up easily when the barter is ready. For something that makes a lot of sense, for others... well, maybe I want the player to actually do something on the scene.
That's what it takes X number of tries is for in my opinion.
If someone is trying to grow a replacement organ in a dead corpse they're keeping on life support for example. Maybe they have to find someone near death, or just died, hook them up in time and then do the weird gross science to them. This isn't just barter, it isn't just time, the player knows the first few times are doing to mess up. (some of the attempts can happen off the scene of course, but they should be represented at least a few times in player actions). Most importantly, however, NPCs should react to the fact he's stealing corpses, someone should come looking for the dead, someone should react badly to the idea, rumors should start to spread about the savvyhead with a garage full of corpses and people should react appropriately to the knowledge/ rumors. All the while you tease the player with new details as they get closer to their goal. This might not take a long time, it depends on the supply of corpses. If those dry up, what will the player do to get more?
Edit:
Basically, if the Failures can affect the story, maybe this is a good idea. Both of the other options... nothing fails. It's just a matter of time or money. In this case, you're saying they MUST FAIL, and we care because those failures have an impact.
You want to build an airplane, you say? It'll take many tries to do that... So who's going to do the test flights?
You want to try to replace the air-filters, you say? It'll take many tries to do that... So what sections of the ship are you going to test that in?
You want to summon a monster and keep it under your control, you say? It'll take many tries to do that... So where are you going to try these summons, what are you going to try to summon, who's going to protect you when it goes wrong?
You want to create a tasteless odorless poison, you say? Who/what are you testing your poisons on before you get it just right?
... etc