Cost of fiberglass enclosure

I have a 2001 Civic and am interested in having a fiberglass enclosure built for my trunk. It will house one 15" Adire Audio Brahma and requires 2.5 ft3 internal volume for the sub. Regardless of shape, materials, cost, etc., sound quality is of the utmost importance. I had previously considered a SubZero enclosure but would like something that meshes with the car better. I will have the enclosure built by a local shop and would like to have an idea of the expected cost parameters before I move forward. I had placed a call and was told I'd probably be looking at between $300-$600 CAD. Mind you, this was from a sales guy, not an installer. Any advice or guidance would be greatly appreciated.     

Alpine Guy, Thanks for the info. Do you think it's better to try and find a fiberglass fabricator with experience building car audio enclosures or go through a shop (ie: A&B Sound)? I'm assuming most of the cost is for the labor, not the materials...

go around to your car audio shops and ask to see installs they have done, and ask for prices. It may be hard to find a profesional fiberglass fabricator depending on your area.2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.