02 P5 roof rack filler caps?

[dd123]

What would happen if I remove the cross bars but don't use the filler cap ?
I don't really care much about how would it look as $150 is too much to spend for some plastic caps.

I would like to remove it to increase my mpg if possible

 

[Celco]

For those of you that have ordered these caps recently from dealers or onlinemazdaparts.com, can you tell me what the final price for all 4 caps comes out to be?

I tried my luck at keeping an eye on the FS board but I don't feel like waiting much longer.