Mobility Scooter battery costs.

13th March 2014. N.S.W. Australia.
I've had my 4 wheel mobility scooter from new for over 8 years and I now have to buy new batteries (for the 2nd time).
When I rang to get a quote I was shocked to be told I would be expected to pay $530.oo
Since then I've been Googling to find out if I can get the batteries cheaper elsewhere. I was told that the $530.oo quote was for 2 x MK 40AH powergel. When I griped about the $530.oo ($30 of that would be for labour to install the batteries) I was told I could get 2 x MK 30AH powergel for $400.oo Still too expensive in my humble opinion but $130 is a big difference when a person is on a pension.
Has anyone else had a similar experience... unreasonably expensive battery quotes? OR am I being unrealistic and the quote I was given is actually normal? Just asking. :-)