I would use caution. There are different grades of carbide. I was told by the owner of Precise Bits many years ago that the price of just the 0.25" shank blanks of the "good" carbide cost a lot more than $8.00! EDIT: Re-reading your post, you did NOT say the new bits are $8...rather, you were referring to the sharpening price. My apologies!
Low grade carbide could shatter/break more easily and won't hold up nearly as well (I'm told). I admit I don't know personally because I've never purchased a super-cheap bit.
If you buy some, please report back with your experience with them.