Most economical way of tiling a huge area for a MOC?

I am working on two halves of a large hangar, 324 studs long and 114 studs wide (for each half). One I want to tile the inside off relatively uniformly, but I need about 1,000 6x6 tiles to do so. They are $0.67/ea (Canadian) from Lego direct in gray, or $0.33/ea (Canadian) in lavender, which I would then need to paint or cover in vinyl (7 rolls of 12"x48", which is not very cheap) to get it to 'concrete floor' colour. I have all the other Lego ordered (30,000 pieces worth) for the rest of the...