AdWords + Analytics, please help calculating RIO on my AdWords

When I calculate my ROI from the AdWords visitors, I’m not getting a positive result yet.

I get paid via CPC, lets say $1 CPC, but I can only get $0.8 income per visitor from AdWords, this makes me a negative result of $0.2 for every visitor I buy. I have set a goal value in Analytics for the clicks, so everything is trackable.

But now, I’m thinking about the returning visitors (about 50%) and how this is calculated.

Does Analytics only track the income of my AdWords visitors for just the session when they have clicked the AdWords-banner, or are the earnings via Goals in my Analytics account based on some sort of cookie time?

I’m thinking:
$0.8 income per visitor for the first visit
50% returning visitors = $0.4 extra for the returns (not being tracked in Analytics from the channel AdWords, but just as direct traffic)

$0.8 + $0.4 = $1.2 = 120% ROI

I would really appreciate some help here!

Thanks in advance