EDIT: To clear this up - installing python on your computer is cheaper, has better support, no limits, is far faster interactively and has really good support.
I know people are going to say "what about iOS/Android" but why the hell would you want to write anything on those devices.
Writing on an iPad is very convenient. I would love to transfer as much work as I can on iPads (from laptops).
And replying to your child:
> I was thinking the same thing. Seems like a niche idea that only people with money to burn and nothing better to do would buy into.
Money to burn, really? $10/month for people in an industry where earning $8000/month is the norm? If anything it might be too low.
For those of us who can't rely on a permanent connection, it's a useless and somewhat risky concept.
If it were $10 a year then maybe we're talking? I mean, I personally wouldn't pay for it, but it certainly changes the mechanics.