There is no profit really unless you would consider paying upwards of $500-1000 for one of these...and working with fiberglass isn't something that I can do on a daily basis. I need to work outdoors and I don't have many free weekend days with good weather to do that.
$500-$600 isn't a bad price to pay for costume sub enclosures...I found a shop that would do my trunk for $750. I have all the subs, amps and crossovers, and they would just mount them in my trunk and cover the fiberglass with carpet. If I had the time I would try it myself, though. Yours looks VERY nice!!