They wouldn't replace anything, at least not for free... this also happened to me years ago. If your bios is fried, then their's absolutely nothing you can do. The backup that's made on your disk before flashing the bios cannot be used as you need to boot before you're able to launch the upload program.
Buying a new motherboard is probably the best thing you could do. Asking Asus for a new firware is not worth it as the final price will roughly be the same as the motherboard. What you can do though is find an unused asus motherboard somewhere, get its bios, put it in your motherboard, crack the updater so that it doesn't tell you it's the wrong motherboard and flash it again with the correct bios... only if you have time to kill that is
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