In novigrad there is a merchant who sells empty bottles at a 1:1 ratio for Crowns, his stock infinitely replenishes with new bottles each time you exit the shop menu but the currency remains, I think he also buys all good and I mean all goods at a 1:1 value ratio for crowns.

So rather than getting 100 something crowns for a 600 crown diamond, you can get 600 crowns or 600 bottles. The reason the bottles are valuable here is because when you sell them to any other merchant with say 4000000000000 crowns in their inventory you get back the 1:1 trade in for bottles. This is how you get around the bottleman having only a few hundred crowns every few days or so.

So after trawling the countryside and looting my way through the game I fast travel to st gregory's bridge and go down to the waterfront, find the merchant and spend about 20 minutes cashing it all in for bottles. Then when I have 6000+ bottles in my inventory which oddly enough only weighs like 60 carry weight (Zerrikanian saddlebags make that nothing) I wander around the town and cash in the bottles for stuff I actually want like spamloads of rare alchemy stuff.



Video has a location for ya