I don't find it difficult, but it's not a set & forget thing as some may think, you need to constantly be split testing ads, trying different keywords, excluding keywords, adding more landing pages, tweaking landing pages, learning new features that google introduces, learning different tricks to get your ctr up and ppc down etc
The full time job was a bit of a hyperbole but I was making the point there's more to it than just a couple of hours here and there.
I've paid upwards of £10.00 per click and as little as .30p...... just depends what your competing for......