Some of you may have heard of an mQx clone called the V929 Beetle (used to be called Ladybird):
compared to the mQx, it is much less expensive, but also has certain "quirks", like automatically flipping when using full stick at the 100% rate.
Anyways, my reason for mentioning this clone here is that many of the parts seem to be interchangable with mQx parts. Some known differences are the Rx board, main frame and wire plugs from the booms to the board.
I can see parts being sold here:
the parts are less expensive than "official" mQqx parts,
but this particular vendor may take awhile to ship things to you.
An example is 4 motors for ~US$16 (V929 pictures show 11 teeth on the pinion gear, but one thing to note, no differentiation between motors for CW rotation versus CCW rotation).
Jul 18, 2012 update: The motors are now differentiated for rotation, but from Banggood's Beetle description and list of spare parts, and confirmed by erdnukel2, the Beetle's motor wires have the opposite color coding from the mQx: red/blue for a CW prop (CW when viewed from the top, also known as an A prop) and black/white for a CCW prop (B prop).