If only used for pictures, low capacity is usually not that much of a problem. 8GB will still get you around 400
raw pictures. Those will start at around $ 15.
If you're taking video, especially raw video, where write speeds as well as capacity matter a lot more.. I would save up for something better :p in that case, you will be looking at around $ 50 minimum
Why silicon power and sandisk only btw?
If you want to go really cheap, this seems to be your best option
Komputerbay 16GB CF 300XHowever, this seems a way better option in the longer term to me
Komputerbay 32GB CF 266xSorry to say I don't have any experience with the silicon power and sandisk ones.. I do own a sandisk SD card, which is fine.
Wondering why and how you got that 7D though :p