If something costs 2.75 it's common to say it costs several dollars. Now, you can be picky, but in common usage saying several hundred for 280-320 km/h is not wrong.

Anyway, birds learn so you can train them to avoid the blades. Shooting something near buildings is risky and loud even with buckshot. Birds can also follow terrain etc. So, while this is far from perfect it's not a terrible or useless idea.