create scarcity or offer bulk buy

could anyone give me some advice on the following two options i am thinking of ( or offer a better alternative if you have one)

I am going to launch a new online business directory, and lets say i have a group of business's within one company i want to make a launch offer to.. This is my current thinking..

1- Offer a percentage off for any of the memberships to that group
2- Offer a percentage off for any of the memberships to that group with a max limit people who can get it
3- Offer something along the lines of this
-100-300 sign up = you pay $$$$$$
-300-600 sign up= you pay $$$$$
-600-1000 sign up= you pay $$$ + 10% advertising
-1000-1500 sign up = you pay $$ + 15% off advertising
-1500-3000 sign up =you pay $ + 100 free impressions + 15% off advertisting

I understand scarcity is a great thing for selling, but i also think number 3 might work as long as a couple committed , then you might get the trickle effect going.. I am not to fussed if i dont make $$$ at the start, because 1500+ people creating content and driving traffic is better for the long run.. Even if they got a massive discount , its still money to grow the site.. The group would have around 2800 clients if that helps in anyway..

What do people think about these options, advice on what to offer.
appreciate the help