Whats the difference between Canon 30/31 amp; 40/41 ink? -

Is there more ink or something, or is the quality just better?

40/41 has a higher print-yield, meaning you can print more pages with these cartridges, hence the more expensive price.

Yes, 40/41 ink is a higher capacity cartridge. It holds more ink and usually you will get a lower cost per print with higher capacity cartridges.

the 40 and 41 have twice the ink.