Here's a hint: Go to town, ctrl-click on Pachinko 10 times to open 10 new tabs on the pachinko. Go to the first new tab, click "10 games" play. Before the animation even starts, ctrl-tab to get to the next new pachinko. Click, ctrl-tab, click, ctrl-tab, click, ctrl-tab, click. 100 pachinko games in 20 seconds. Then go and close all the tabs you just made. Easy!
I love to see people with no idea tell devs how easy it'll be to make some "small" change.
HH tracks individual items in your stock, so when you click "sell" it doesn't just tell the server "sell one of my Greaves" or whatever, it says "sell my greaves ID #62892592". This stops cheaters from double-selling. So it's not as simple as you wish it was, they'd need a new API endpoint to handle a whole new "sell everything" action.