My 2 cents:
I think they should up the minimum to 10 GB free storage, this allows free coverage for icloud backups with both iPhone and iPad and a few documents considering the average iCloud backup is around 4.5 GB for me. Probably for most as my wife's and daughter's backups are around the same size.
You can't just offer free storage either. Datacenters cost a lot of money, think about the utility bills, a typical server costs around $30 a month to run. Now imagine 100,000 servers in a datacenter and then imagine 10 datacenters. It scales pretty quickly. I'm sure their network to each datacenter is at least 5 digits each. Now lets include the payroll for those employees managing those servers. Oh and now we need running water for the employees, and toilet paper, and paper towels, and.... see where this is going. I wouldn't be surprised if each datacenter costs 10 million to run each year, and that's after the initial 100 million investment in the datacenter. Now Apple did save money with the solar panels, but think about the upkeep of those servers, not every server makes it past the first year, with as much as they work, they may not make it past 5 years, which means they've been replacing $50,000 servers while users are complaining about the $2 price to upgrade. Google and Microsoft are cheap because they sell aggregate data to 3rd parties. They assist companies in marketing especially for you. Apple doesn't do that which is why you pay the premium. I'll gladly pay them the $3 a month for 200 GB.