I don't like to give absolutes as there are always personal preferences which will come into play and various metrics one can choose. If looking at performance criteria such as GD, SPL, THD, SPL/$, etc, then yes, ID subs (SVS, JTR, Seaton, Hsu, Rythmik, etc) can better many/most/all of the above mentioned subs.
As for profit, I don't expect anyone to run a charity. Materials, R&D, labor, packaging, shipping, veneering/finishing, QC, marketing, overhead, credit card/paypall fees, web server/site fees, etc., all come into play. If one is looking at DIY, one should also take into mind the cost of the tools (which may or may not be amortized over various projects), labor costs (I don't work for free for others, why should I not count time spent when working for myself? If it takes me ~8+ hours to buy materials and build a box, what is the equivalent $ in wages? ), work space costs (people forget that they are making things at home, a cost they are already carrying. Try making dozens/hundreds of subs at home every month and you'll find you are quickly running out of space).
I am sure a great many people find a great value in DIY, but the added costs that surround each project tend to disappear in some comparisons.
"Every loaf of bread is a tragic tale of grains that could've become beer.......but didn't...."
"If it works the first time, it's not high end." ~ Harry Pearson