Tiny Tina's Wonderlands

This trophy is a lot simpler than it sounds, because there are at least 4 ways to get it done but do note it isn't cumulative:

1a: Solo Duping: There are many duping exploits of varying complexity available but the following simplified version only needs 1 controller and is far less likely to be patched out:

1. Gain full access to the Chaos Chamber by finishing the Epilogue. Note: You can do this at Izzy's Tavern but it's much slower due to the vending machines being a lot further away.
2. Fill the Bank with as much loot as it will hold, then mark everything as junk by pressing  on each item until a little red icon appears in the top right-hand corner of the item card.
3. Save and quit the game, then backup your saves to the PS Plus Save File Cloud (a USB drive works as well but it is slower to locate and retrieve your files, especially if you have a lot of other saves on it as well).
4. Reboot the game and reload your save, then go to the bank and empty its contents into your Backpack. Now go to the nearby Mystical Magicks vending machine and press  to quick sell everything. Once you've completely emptied the bank and sold the contents to the Mystical Magicks vending machine, save and quit the game again.
5. Now instead of redownloading all your saves, choose the option to manually select the file you want to download, then tick the box next to the "User Settings" file and choose to download it. Caution: It is imperative you redownload the "User Settings" file before buying any upgrades, else you will reverse the purchase you just made and have to redo the exploit from scratch.
6. Reboot the game and reload your save, then check the bank and see that all the items have returned but you still have all the gold you made from selling everything before restoring your save
7. Repeat steps 4-6 until you have the desired amount of gold but make sure to backup your saves every so often in case something goes wrong.

The more Bank and Backpack slots you have, the more gold you will make with this trick. Credit for discovering this newer duping exploit goes to myself.
 
1b: Co-Op Duping:
 
Here's a Co-Op Duping method, courtesy of Dreggit:
 
What is most important, is this doesn't involve backing up your saves to the PS Plus Save File Cloud:

1. Give your alt account character all the money
2. Trigger an autosave with your main character in Brighthoof by walking by a fast travel station
3. Trade all money to second controller character
4. Quit the game with the second controller to exit split-screen mode
5. Close the via the XMB.
6. Reboot the game and have the second character join your lobby
7. Rinse and repeat steps 1-6

When the second controller quits the game in this way, the game saves the second players inventory but not the primary character, effectively "duplicating" the money. This is faster than uploading/downloading a cloud save every cycle.

2: Trade with a friend: If you know someone who has a million or more gold on them, use the trading system to swap something of yours in exchange for it.

3: Play legit: Despite a million gold sounding like a lot, it really isn't and you will get it by the time you reach Chapter 7, provided you sell everything you don't need and open every chest you find, along with spending as little as possible. Increasing your Backpack carrying capacity will also help with this, because then you can carry more stuff so more items = more cash when you sell everything. You can quick sell items by marking them as junk in your Inventory by pressing , then pressing when looking at a Mystical Magicks vending machine. Once the DLCs are released, you will have more places and opportunities to earn Gold so both this and the two Inventory related trophies won't be as big of a grind. 

Note: Starting March 3, 2023, with the release of the 1.0.6.0t Hot Fix, every 5 months for 5 weeks, there will be an "Optional Profits Mini-Event" where you will get a lot more gold from enemies in certain locations so take advantage of this when it happens. See here for more information: LINK

4: Farm the Chaos Chamber: The Chaos Chamber opens up after you finish the main storyline and will let you unlock Chaos levels (which are this game's version of Borderlands 2's OP Levels and Borderlands 3's Mayhem Mode). Each time you earn a new Chaos Level, the amount of Gold, XP, Luck etc. you can earn, goes up by a small amount. You will also make a decent amount of Gold by selling all the junk you pick up whilst in the Chaos Chamber. To maximise the amount of cash you earn, do Extended Runs on the highest Chaos Level you have unlocked.