The crewing level does vary!
The A319 and A320 have at least 4 crew and the number is actually regulated depending on which trip the aircraft is doing and obviously also the load. For an AMS you would have 6 crew (2 in EC and 4 in ET) due to the short flight time and the service onboard.
Go to LGW and you will see that the aircraft always has less crew. Their 777 has either 10 or 11 crew whilst LHR has at least 11 and at the most 13.