It would be nice to know what the competition involves - what do people have to do to win it? And what's the prize/reward?

Assuming it basically means that people get some sort of reward for their efforts (possibly financial but not necessarily), perhaps we could say something like:

"Hard work brings rewards"

or

"Get out [or get back] what you put in"

e.g.

"Want to get out what you put in?

Are you fed up with putting in 100% effort but not reaping the same level of reward? If so, read on."
http://www.gumtree.com/london/14/6516814.html

"Hard working families are caught in the horrible reality of the two income trap created by high taxes, high housing prices and the myth that hard work brings rewards."
http://news.bbc.co.uk/1/hi/uk_politics/vote_2005/frontpage/4...

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Note added at 1 hr (2007-01-09 16:41:45 GMT)
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The other thing I'm wondering about is, is there a suggestion that laziness will be punished, or is the implication simply that hard work will be rewarded? If it doesn't mean laziness will be punished, I think that will rule out quite a few proverbial expressions like "reap what you sow" etc. because a number of those can have negative meanings as well (i.e. if you do something bad, something bad will happen to you - or if you do something good, something good will happen to you).