It is really expensive...
But they can ask any price for them, really.
DIY custom TOHs won't be cheaper though.
I have read the documentation, it is nice that You can make an app to download as TOH snaps on, and works only with that TOH. You can sell an app or service whit a TOH, but I am not sure if it is going to be a succes.
Anyway, new opportunity:
Sell Your app with an NFC tag, only the one with the NFC tag can download and install it from the store then.
But it is quite awkward to install as You need to remove the TOH to touch the NFC for installing.