Ask HN: Why are gambling adwords the most expensive?

I have recently come across a post: http://visual.ly/most-expensive-google-adwords-keywords-uk-data

which basically (tldr) says that gambling content is the most expensive (upto £80 a click). So my questions are:

[1] Why are they so expensive? Is the content? lack of gamblers? rich casino/betting houses? [2] What other options do you think are viable other than adwords?

Disclaimer: I ask the second question because I run a small webapp for the UK which displays current top sports betting tips (i.e odds comparison) + bonus codes/free play - and I am considering advertising via "some form of adwords".