True SQ costs more, there's no doubt about that. I Love JL, but their pricing structure is something I wish they would change. Especially since they haven't updated any of these in like 10 years. That said, any of he high quality Subs will cost a lot more than the Alpines, Sundown, and DB's. There's several high end brands in Europe for example that are very similar in pricing to JL.I'm not looking to do JL or change my size in subwoofer. The cost of getting a new JL 8w7 I could have a new sundown SA8 with custom ported box. So I'm sticking with just a single 8 and going by those dimensions
Europe has far more focus on SQ than the US Car Audio market does. US fans have always focused on SPL in both design, sales, and competition. But for SPL you focus on how much air you can push per Watt of power used, and how much wattage you can sustain thru VC Cooling techniques. SQ requires more precise control of the cone both in remaining linear thru its full extension and also the speed in which you can stop the cone preventing residual vibration. And that's honestly harder to do than high SPL is.
I'll say this before I leave off on JL. Their Subs, especially the W6 & W7s hold up for a long time as long as they're not mistreated (left outside or in a very hot storage unit where it dries out for example). That's why there's a Big used JL equipment market. So if you ever want to try one of their Subs the used market isn't a bad way to go when you're ready to step up to a higher quality musical driver.