This can go pretty insanely high.
Key points
1. This is a Bm deck, so we have a lot of free villages.
2. We have Mandarin as a kingdom card so we can play all our Igg multiple times via Bm -> Igg (gain a copper) x10 -> buy cards that cost >$3 (remember that a single Quarry can make pretty much all the non-actions except Fool's gold, Tunnel, etc. viable for Mandarin gaining).
3. We can redraw our Igg with something good for big draw (e.g. Madmen from the Bm deck; Cellar all the copper we gain & keep and hand; Apprentice a few colonies).
4. We can return Mandarin to the supply with Ambassador (optimal play gets hinky with non-solo play, but we should be able to do this a huge number of times even with cooperative 2er).
5. We can reuse Bm with Procession/Rogue/Graverobber
6. We juice the whole works with Ventures so we can draw back the Igg during Prssn->Bm plays.
7. With Princess & Highway in play we can use the gainers from the Bm (e.g. Iw, Armory) to get the 10th cards in a lot of piles.
So we want something like Play a single Haggler -> Prssn -> Bm (play 10 Igg, gain - don't play 10 coppers, play a Quarry, buy a $4, gain a Mandarin, top deck 10 Igg & 1 Quarry; play 10 Ventures -> play 10 Igg, gain another 10 C, buy a second Mandarin) -> Graverob the Bm back (note Quarry is not "in play") -> draw everything -> Amb (return 2 Mandarins to supply).
So on net this whole shebang has cost us exactly: 1 Prssn, 1 Amb, 1 Graverobber/Rogue, and 1 monster draw card (10 Madman, Cellar, Storeroom, Xroads, Apprentice&Colony)
We could optimize this a bit with multiplicative play of Prssn and then gaining back some Amb by trashing them with Prssn, I don't have time to do that so let's stick with the simple case: we do this 10 times. This gives us 10 x 20 gained coppers = 200.
Okay, now we have 10 more plays of Bm, until we run out of Mandarins. So this is another 100 coppers gained.
So what cards need to be in the kingdom?
1. Bm
2. Igg
3. Graverobber
4. Mandarin
5. Prssn
6. Amb
7. (likely to get enough draw) Xroads (bane)
8. Kc (likely to ensure enough actions)
9. Venture
so we need 2 more slots.
Well we can put in Counterfeit. And play another 20 Iggs for another 20 coppers, but a better option would be using Rogue/Kc/Tr to build a very finicky multiple play chain to trash Amb's and Prssns as well as Bm's & gain everything back to play again. Band of Misfits would also work as a filler card allowing us to effectively double any one of Bm, Amb, or Prssn.
Ultimately, I'm pretty sure we can do the whole Prssn -> Bm (gain Mandarin x2; using 10 Igg then 10 Ventures) -> Amb (return Mandarin x2) at least 20 times and maybe even more with full on optimization.
So for the non-optimized run through, that should be 320 coppers gained. For an optimized setup, likely north of 500, perhaps as high as an order of magnitude more (though this is doubtful). The top end is hinky (at some point you run low on huge draw and even every village from the Bm deck isn't enough); and you are trying to optimize a lot of cards (you want to double/triple play Prssn/Graverobber, but you need stuff in hand/trash to make that work).