I'm going to add my response to your justifications...
1) There is no difference between a Axle Back Muffler and a Universal Muffler from Borla... Borla just did all the welding for you, and pre-set the hangers.
2) Of course the sound is going to be different. You were with Celicas. Compare your Borla Axle Back to a Custom Borla / Magnaflow on a 10th Gen Corolla with the same engine and same pipe diameter. Then report back. the 2ZR-FE is a very quiet engine compared to the older 7A-FE, 3S-FE, 3S-GE, 3S-GTE, 5S-FE found in those celicas.
3) Yes it would be easier to do a DIY, but at the cost of a couple hundred bucks?
4) Borla made a pre-assembled axel back that fits your car using a Universal Muffler from their catalog. It is not like they designed a BRAND NEW muffler for the Corolla Specifically. They just pre-bent the pipes for ease of installation. Borla did what ANY muffler shop can do.
Response...
1.) You are absolutely correct. Seeing as how I can not weld, I appreciate the fact that they did so.
2.) You are again correct. I was with celica's however I have compared the following (Borla "Custom" vs Magnaflow "Custom"; Borla Axle-back vs Borla "Custom"; and finally Borla Axle-back Vs Magnaflow "Custom") and IMO I prefer the Axle-back Borla Bolt on. It just sounds better.
3.) I do think that it was a bit pricey, but in the end... it was my money.
4.) Borla might have "pre-bent the pipes for ease of installation", but they did NOT do what ANY muffler shop could have done IMO. I personally do NOT trust muffler shops because I have had bad experiences with them. From rude customer service, to shoddy craftsmanship. I also find the following statement argumentative...
"It is not like they designed a BRAND NEW muffler for the Corolla Specifically." considering that it is SPECIFICALLY for the 10th gen Corolla, and it was BRAND NEW. Not to mention, Borla had to put in a SPECIAL work order to have mine made. (meaning they didn't have any in stock).
Either way, you have your opinions, and I have mine.