Earlier quoted context omitted.
Why not buy the non-free plan for a week, then cancel? Or email them. They might use PayPal, perhaps you could transfer money in there if you know the right account.
Most important reason: laziness I am not going out of my way to give them money. However I am perfectly willing to pay when they change their price structure. [For dropbox I found their prices per GB are almost double of cheaper competitors. They could charge much less per GB if they would get money from more customers]
Granted, the service is very different, and Google is ever-so-slightly larger. It's still a big jump.