Did some computation here...
In order for Shopify to break-even with his $100K, they need 4,167 ($100,000 / $24 per month membership fee ) new registered paid stores.
After that 2 months contest, MAYBE some of them will bail out with the membership.
At the end, this contest is a very good marketing strategy to pull-in new customer.
divide by 6 (the contest is six months, not 2). That means 833 people for six months, some of whom will become successful and keep doing it. Then there's a 2% transaction fee for the entry level shop. Then, some will choose premium plans.
If they even get 100 successful new businesses (that last two years and end up on the 60/month plan), they've paid it back with interest - the unsuccessful startups are just a little extra. (And, they get people who will use the service as customers and tell their friends!)
After that 2 months contest, MAYBE some of them will bail out with the membership.
At the end, this contest is a very good marketing strategy to pull-in new customer.
Nice job Shopify.