aschroft
There are so many variations in the payscales that it is hard to give a simple answer.
Here are some snapshots which I am basing on you wanting to join as a DEFO?
US A(USAB) scale is 40.8% higher than UFO(US) for 1st year FO.
Aus A scale is 40.5% higher than UFO(AUS) for 1st year FO.
EUR A scale is 41.1%higher than UFO(EUR) for 1st year FO.
The differences reduce over your career. By the time you will have been here 20 years you should be around SCN3-5 where the difference is down to 20% in favour or A scales. Based on the 2008 payscales the minimum difference you will ever achieve is when you get to SCN 17 which will be in about 32-35 years - then you are only around 10% behind A scales!