The reason for having only 1 $5 buy-in/week compared to a 2-3 $2 buy-ins per week is that the turnout on the $5 buy-in is going to be quite high as it's easy to spare time for one tourney than 2-3. Moreover you are spending approx $5 in both ways, so the higher buy-in should keep you from joining. Including the freerolls gives you an extra opportunity to score points and win good money that you can spend for the buy-ins
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This may look complicated but after you play 1-2 games, this will all be second nature.