they usually cost more. creating fonts takes more time then most give it credit for. yeah there isn't any hard grueling labor like a mason would have to do, but someone sat there perfecting and fine tuning most of these commercial fonts you see today.
good grief do you have any idea what the majority of us have invested in fonts? i simply do not understand all these people that think these things should be free. pass the cost along to your client and add another font to your arsenal, it's the professional thing to do.