Are you crazy? It's still quite easy to get the Iridum for a Matterfabricator, no Platinum + Rich Slag shenanigans needed.
Step 1: Take your Jetpack to the End and mine 8 Sheldonite ore. Sheldonite is found in the floating asteroids, usually 2-4 per asteroid, so you may need to check 4-6 Asteroids before you find 8 ore. It is difficult to see as it has only a slight yellow texture shift from the default Endstone texture, but it's usually floating in space all alone, so not too difficult to spot.
Step 2: Process your Sheldonite in the Industrial Grinder with Mercury Cell as the liquid input. You get 12 Platinum Dust and 1 Iridium Ore per 4 Sheldonite, so 8 Sheldonite will give you 24 Platinum Dust and 2 Iridium Ore.
Step 3: Take 16 of the Platinum Dust to your Centrifuge and create 2 more Iridium Ore.
Step 4: Take your 4 Iridium Ore and compress it to ingot, then craft an Iridium Plate using the Rolling Machine and Implosion Compressor. Then create the Lapotron Orb from the resulting plate.
Step 5: Smelt 4 Platinum Ingot from the leftover Platinum Dusts. Create 4 Energyflow Circuit from the 4 Platinum Ingot.
Step 6: Create the other components of the Matterfabricator (HV Transformer, 2x Teleporter, 4x Highlyadvanced Machineblock) then combine into a Matter Fabricator.
If you didn't kill the Dragon yet, just bring an Ender Pouch and store your inventory, then fall out of the Void (this kills the Steve) to get back to the Overworld. You can use a different Ender Pouch or Ender Chest set to the same color combination to access the saved inventory once you're back in the Overworld.
It takes longer to process the ore than to mine it in the first place... I got 1+ stack of Sheldonite after an hour or two of mining in the End, which yield 40+ Iridium Ore when fully processed... enough for 10 Matterfabricators.
I just did some testing in MindCrack v8. This magic carpet ride is over. Rich slag is down to 5% for most ores from 20%. Gold ore is at 10%. Additionally you get 2 shiny ingots rather than 3 now so the multiplication factor is gone and it uses sand instead of rich slag + platinum dust. If my math works out the only way to get a matter fabricator now is blind luck finding an ore in the wild or industrial grinding 384 ferrous ores. I have to say I am not please with this prospect.