The straight flute hand-router bits I have are certainly not cheaper. I like Trend cutters, and you can see the price list here for straight 2-flute. These prices are not uncommon. Trend also make spiral bits, but strangely they only maker larger than 3mm dia. with a guide bearing attached?

Anyway, you recommend spiral cutters for CNC. Should I use a different type of bit for routing hardwood / MDF than for aluminium and other soft metals? I'd intuitively expect metal cutting bits to take a more shallow angle of cut.

Is there a worthwhile difference using HSS for softwood or should I just stick to carbide?