Dropbox now charges about 12 cents per GB per year.
If one accepts the slight inconvenience of using the free plan of each major service (Dropbox, Google, Microsoft) which requires him to split his data 3 ways (for example family photos on Google, personal on Dropbox, the rest on Microsoft), he can use close to 50 GB for free. (Note that Google docs do not count towards that limit, so were one to store all his docs in Google format on Google drive, that wouldn’t even count).
Those who want to pay can get a large amount of storage cheaply. Others can get a very decent amount of storage for free. It seems clear to me that the cost of storage will not be the main reason to switch to the SAFE network and giveaways will be unproductive.