What about if, for example, I had one of each discount card (10, 20 and 30). Does the game only accept the highest value discount card?

going to bed now, will reply in the morning, thanks so much for everyone's help and I hope it helped others who were wondering the same thing.

It will take the 15% off with the buff and then the highest discount card. You can't use multiple discount cards at once.

The buff exists because we used to be able to haggle for a fifteen percent discount, which required doing math in your head. When haggling was removed the mathematically inclined of us complained bitterly.

The buff is to become more rare to activate over time and to stay active for less time. If it seems that you see it less nowadays, that is intentional. It is 's intention to remove it altogether. Do not rely on it staying around.

Discount cards do not stack with other discount cards. It took me six years to pay off my 30 percent one. "You have saved 313,407,805 sP using your discount card." About a hird of a billion overall, around 30 million per year..

Thank you for asking this question and thank you to everyone who has replied! I was also really confused but this has now been cleared up. :D

You're welcome! :)

1. Discount cards do stack with the 15% buff
2. Discount cards do not stack with each other, only the highest value of the ones you have will work.
3. The 15% buff will eventually be removed from the game
4. Discount cards give a permanent discount as long as they're always in your inventory (recommended to lock them)

These appear to be the answers? :) Thank you so much everyone for all of your help.

I'm going to ask for this topic to be locked now that it has been resolved. :* I hope it has helped other people.