I have friends who have a package like this in USA ... they share 2gb data between 5 of them plus their calls / texts but it costs them 70 dollars a month .
So they're paying for 400 MB for $14 (£10.66) per month per individual. Giffgaff has 500 MB for £5 ($6.57) per month per individual, which for 5 people is £25 ($32.83) per month, plus an extra 100 MB each. Each of them having the £10 3 GB (+1) goodybag works even out less (£50 = $65.66).
So it's costing them more than twice than what it would if they were in the UK on individual plans, or they could get 10x the data for the same price here. Are they getting ripped off, or is the US an insanely expensive place to have a phone?