To throw in a different opinion... $150 is not required. A DVD is not required. Windows 8 is not required. Legit or not makes no difference. VMware Fusion should not be required, either. Because I've fixed it before without any of those.
Try to use an ISO of Windows 7 with a USB key/hard drive. Boot Camp Assistant can use your ISO file to image the USB key, and when Boot Camp Assistant finishes and reboots your Mac, it should install on the new "BOOTCAMP" hard drive partition from the USB key.
I've done this before on my 2012 MacBook Air w/ 10.8.2, which of course has no internal optical disc drive. Note, however, that the USB key/HDD is not 100% reliable for everyone. Sometimes, for example, you need a USB hard drive or different USB key. Sometimes you need to remove the "BOOTCAMP" partition and run the Boot Camp Assistant again, multiple times, until it is magically blessed. This happened to me -- it worked the 4th time through. I wish I knew why.
"No bootable device - insert a bootable device and press any key" does not have to do with the ISO necessarily. This can be caused by an error with your internal hard drive's MBR, for example. Your Mac should be detecting the Windows disk (whatever media it is using) as bootable. Otherwise, it cannot load the Windows installer. Any time that Windows 7 or its installer cannot be booted, it will cause this error.
I'm encountering this error myself on a different Mac right now. From gpt and fdisk and Disk Utility, the partitions and boot record look normal. The USB key is the same one that I used before; but it's not working now on this 2010 Air w/ 10.8.2, for some reason. Did you find any more information?
Fixed. Hope this works for you.
Try installing Windows 7 from an older (but popular) USB key. Borrow a friend's if you don't have one. Try to get one made before your Mac shipped.
Older Mac firmware may not have support for newer external drives. Firmware loads after hardware sanity checks, but before booting the OS, and therefore if it doesn't have good support for your external drive, it won't be able to continue the chain of execution into OS/installer boot. Older Macs may not be able to detect as blessed/bootable and load the file system from a newer (or otherwise unsupported) external drive.
The 2010 Mac Book Air would not boot the "WININSTALL" disk of the Windows 7 installer created by Boot Camp Assistant on my newer Lexar USB key, but the 2012 Air had no problem. Switching to an older USB key solved the problem on the 2010 Air.