[Asus Transformer TF700] incarceration:
If this were the case there would be more than just the occasional person(s) complaining about such an error or issue. They charge the fee necessary for parts and labor, parts and labor for electronic devices (especially when rendered by the manufacturer and are on something that is CLEARLY out of warranty) is NOT intended to be inexpensive. Yes, if you had "one bootloader version lesser" you would be able to recover from the brick, but do you think that would've even been the case had you known that? I don't. You did a factory reset on a rooted and unlocked device, that, other than maybe OTA updates (on things such as rooted phones) in such a scenario is probably the worst thing to do. The fact it's "not the first time asus has treated" you "poorly" means you haven't learned your lesson from the first mistake you made. Next time, do things slow and carefully, don't jump right into something you're not aware of 110% of the outcomes of everything you do along the way.

You rooted and most importantly YOU unlocked the bootloader, as all the warning labels say on all custom content EVERYWHERE and all associated with customizing your Android device, you NEVER "factory reset" ANY device. How can you blame the manufacturer of the product that you yourself caused to malfunction?

I'm sorry that you caused this to happen due to personal negligence or ignorance but don't blame it on someone else or some other entity such as ASUS. Next time, be more careful and read all warnings twice or thrice.

You're now rehashing all of this once you find out the consequences of your ignorant actions. Just take it in stride, learn from it (more than just saying cliché sayings of "lesson learned"), actually learn from it, and move on with life. It's only a tablet and if you can't afford the potential consequences of rooting and unlocking, don't do it and use it stock; it works great stock anyway.

This is total and utter non-sense. I have a rooted, and unlocked TF700T and it works FLAWLESSLY. Also, to note, I DO NOT have and never was able to use NVFLASH, so I have no safety net.

I AM careful with EVERYTHING I do to it, BEFORE I do it.

Maybe you should try the same instead of blaming a company that is helping its customers (typically more advanced customers that are trying to utilize the tools they release such as the bootloader unlock tool.)

ROFL @ the notion that it's "trying to convince you to factory reset" because it's "slower" than before. The whole POINT of unlocking your bootloader is not just to do it for the hell of it, same for rooting; they both have their purpose and NEITHER is just to do it for the hell of it and leave it. The purpose of rooting but NOT unlocking is to utilize apps and such that require root access. The purpose of unlocking is to flash custom content such as a recovery, kernel, and custom ROM.

Take the mistake of ignorance on your part and move on instead of blaming something that obviously isn't happening to everyone because it hasn't happened to me so it's not something they're implimenting in their software to do to get us customers to void our warranties, notice our devices "slowing down", factory resetting the device (which you should never do after rooting or unlocking ANY root device), and then bricking your own device to send back to them for repairs.

As far as the costs and reasoning to needing a new mainboard\motherboard after bricking your device, even it being just a software issue, is because it's also a hardware issue. I assume the software has to line up with hardware IDs (ie: on the mainboard) and to do that, they have to replace the entire board. It may also be because the bootloader is physically stored on the mainboard, kind of like the CMOS chip on a PC motherboard that stores the BIOS, and if you screw up that bootloader, it can't be replaced by any means efficiently necessary but swapping out the boards. In the case of a bad BIOS flash on a CMOS chip for a PC motherboard, if it's not a socketed CMOS chip, you're boned and have to replace the board as well.

Learn about the technology before bashing a company that has gone beyond what most manufacturers do to enrich their customer base's experience with their devices (such as allowing the bootloader to be unlocked).

1 thing I do agree with, it should be reversible, but I assume this isn't allowed because crafty people could reverse it and THEN send it in and it'll still appear in warranty and if it's already reported back that you used the unlock tool, what's the point of reversing it anyway if they have a record of that? They won't care that it doesn't say "This device is unlocked." because they'd have the record of you unlocking it in the first place.