So as described here:
http://prepaid-data-sim-card.wikia.com/wiki/France
You can get the 2 Euro package, use up the 500 MB and recharge 2 Euro at a time for up to 2 GB of 4G data over 8 days.
Has anyone confirmed whether tethering is allowed?
What about the starter kit price for a nano SIM?
If you can't use foreign credit cards for the recharges, how do you recharge online, use top-up voucher codes?