Cams alone will not give much in terms of extra power and they certainly won't improve your fuel economy. What you are likely to find is due to the minimal increase they will give being at the upper end of the rev range, you will be reving it harder thereby using more fuel not less. Adam at Z1 is the guy to speak with about tuning NA engines, but essentially it's not cheap because you need to do the whole lot, heads, cams, headers, etc, to get any real benefits.