All-in-ones and branded tanks are definitely more expensive. My juwel 4ft, cost $1.2k. Where as (depending on who you use) a professionally(?) made tank at the same size would cost about 150-300. I guess anything with a high price is going to be good quality(if you do your research around different shops), as if it breaks, they are going to be liable for it. (If it's under warranty), Not to mention that brands making bad tanks risk ruining carpets and killing the poor fish.
I'm no expert on the types of tanks, just my 2c.
HTH