What kind of price difference for kennel sizes?

BA charges based on kennel sizes.  I've got (3) kennels that are 26x18x18 - perfect for my big guy and oversized for my 2 girls.

Apparently, they aren't going to measure anyone.  They are just basing "correct" size on ear clearance and lay down room.

I'm trying to decide if it's worth it to run around looking for smaller carriers (with metal bolts etc) or just bite the bullet and pay the almost $1600.

Does anyone have numbers on the difference between, say a 200 and 100 kennel?

PS.  For people who are saving for moves, over estimate everything!  I have been planning for over a year and circumstances out of my control (emergencies, the economy, people who don't communicate in a timely manner, etc) have left me well short of my $$ goal.

We were quoted $1499 on Virgin for 2 "medium" vari kennels with dimensions of 28x20.5x 21.5.  I have a 22lb monster cat and he needs this size kennel and a smaller cat who will have some extra room. 

I can't say what BA charges but I am flying with BMI and below is the link to where I gave my exact details of what I was quoted thru them. 

http://talk.uk-yankee.com/index.php?topic=44379.msg633095#msg633095

When I flew with BA, they wanted to know the dimensions of my kennels when I booked, but the actual fees were calculated based on weight, not size.  Of course, this may have changed since 2006!