Seems like everybody recommended to start with less competitive countries. It's make sense.
The problem is the ratio between the CPM and the Payout.
If the CPM is 20% lower, the Payout is 70% lower.
That makes it X2 more challenging to make it profitable.
I'll give you Real Example:
- Exact same offer, exact same traffic source.
GEO: BE
CPM: 2.95$
Payout: 0.8$
GEO: AU
CPM: 3.75$
Payout: 2.8$
Let's send 100,000 Visitors: (Assuming that the CR, CTR and everything else is same)

Cost: 375$
Revenue: 485$ (30% ROI)
Leads: 170
Visitors Per Lead: 588

Cost: 295$
Revenue: 385$ (30% ROI)
Leads: 340
Visitors Per Lead: 295
Result: You'll need X2 More leads with BE.
(Obviously the numbers are not static, this is just an example!)
Question: How you can possibly recommended to start with less competitive countries?
Yes, the CPM is lower but the Payout is also much lower.
According for this numbers, It's will be X2 Harder.
It's like 50% from your traffic goes nowhere, or 50% Increase in the prices.
I probably miss few things, What do you think? 
- Matan
One advantage on these untapped geos is that their database is pretty fresh. Which means much higher conversion rate most of the time.
In countries like BE, NL, SE, DK, NO, FI you should get even higher pay outs than in AU as the value of user is higher in these tier1, high-GDP spending power countries
What julien said. It's the conversion rate that will make all the difference. Database being fresh is a big factor. Another reason may be because those geos aren't as blind to ads as the rest of the world is because they haven't been bombarded by ads left right and center.
Amy
as our friends here mentioned: a payout tells you nothing without knowing the CR! less competitive markets usually come with additional advantages. smaller budget needed, more stable data, less stressy to work with (bidding changes...).
Thank you very much. Later I'll work with other geos so I can see the difference. 
Coincidentally - I also talked about this in another post yesterday. For your reference:
http://stmforum.com/forum/showthread...l=1#post248885
Amy