Doesn't add up...
"Pogoplug Cloud is a Dropbox-style service: you get 5GB of online storage space for free, but you can expand that to 50GB or 100GB for $10 (£6) and $20 (£13) a month, respectively. That's what Dropbox charges, and is rather better value than Apple is offering with iCloud: £70 a year for 55GB."
50GB for £6 per mo = £1.44 per GB per year
55GB for £70 per yr = £1.27 per GB per year
So Apple's offering is actually better value (who'da thunk it?) if your figures are correct.