FS, at the bottom end of the market price wise for decent performance is not where most of us here are coming from. I've been telling people on forums for 15 years that the best value for a speaker (not sub) is second hand, not DIY. There is a threshold that once crossed, DIY becomes far better value. You can't beat volume manufacturer economies of scale as a DIYer; I thought that would be obvious.
When you want performance, such as being able to play at reference levels, the off the shelf units are generally much more expensive than what you can make yourself. What would a commercial design of equivalent performance to a dual LMS5400 cost? there are JLs in this league at 5 figures - with some good shopping I could do it for 40% of that (in the US) and probably even better here (Australia) because of importer/dealer gouging.
Similarly for mains, where can you get a commercial controlled directivity speaker for anything like what you could build a 3/4Pi or a SEOS for?
the other thing you'll find here is a much higher level of technical knowledge, and actual measurement of devices, such as Ricci and Illkas sub testing, rather than someone merely saying 'this is good'. Add to that the far more common here room measurement, multi subbing, controlled use of EQ (rather than merely automatic such as Audessey etc), real amplifiers etc, and DIY thoroughly bitchslaps commercial above a fairly modest threshold.
Plus there is the enjoyment of the build, the pleasure in saying 'I did that' and most of all the learning, rather than mere consumption, in the DIY community vs the audio proletariat.