What better sources of teeth and scales are you referring to? Harvesting them from wandering beasts seems extraordinarily tedious and time-consuming. Converting to them from fur requires an incredible amount of fur.
The one time I did buy alien alloy from the store, I didn't have too much trouble farming 750 scales from big lizards, though. I could bring in 30 or 40 scales per trip. I didn't time myself, but the trips themselves couldn't have been more than a minute or so in duration. It was definitely tedious, but not totally unreasonable.
Traps are a poor source by comparison -- 20x to 40x less efficient per time spent. Admittedly, they're passive. Sort of.
I guess it depends on what you consider unreasonable. I don't usually play games w/ a large amount of grinding.