The only reason to get expensive cards of the Sandisk variety is if you intend to hold your finger on the shutter button and rattle off multiple exposures as in sporting events etc. There is nothing wrong with cheap cards if you just press the button once or twice or so, then move on like most of us do. You are no more likely to lose pictures on a cheap card than you are on a Sandisk.
I have 15 4gb CF cards, only one of them being a Sandisk, an Extreme III. This was the first 4gb card that I bought, when under 1gb was the norm. It cost me around £150 some years ago. It has been no better than the cheap Dane Elecs and similar that cost me under £20. I've even done 5 or 6 shots in quick succession on the cheap ones without being held up by writing, but that could be down to the Canon as much as the card. In fact, one of the Dane Elecs has been through the washing machine and still kept all the pictures. But then it should do anyway. Not one of the cheap ones has let me down in any way over 5 years or so.
Cheapest options will probably be on 7DayShop.com