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laner-
Are you not mixing up calories of cooked rice by weight with price of dry rice by weight?
Always nice to see somebody paying attention. Yes, you're right, so you only need to buy 400g of dry rice costing 8p (when bought by the Quintal of crappy Government Quality) to get the 124kJ net (generator output less cooking input, assuming you use best practice for cooking), which is about 0.7p worth of electricity at UK domestic prices.
Basically, food is very expensive in terms of energy content compared with oil or gas, and as much as we love the efficiency of a man on bicycle, he turns out to be pretty crap as an electricity generator compared with a good combined cycle gas power station which can exceed 50%
gbj_tester
In the target markets, people who are too poor to buy fuel are frequently also too poor to buy enough food, i.e. they are just about getting by in terms of calorie intake. If you ask them to provide 0.25kWh per day to power their lights, they would need about (0.25×1000×3600)/(4200×0.2×0.7)≈1500 Calories per day of extra food. The numbers in there are 0.2 for human efficiency and 0.7 for generator efficiency, there's nothing in there for drivetrain or battery/charger/inverter losses, so the real number will be quite a bit higher. If you're eating 1500 Calories a day because that's all you can afford, more than doubling your intake to get some electricity doesn't seem like either a priority project or even a sensible allocation of resources.
1500 Calories is about 1kg of rice, and you need a minimum of 776kJ of fuel to cook it to get your 900kJ of usable output.
Mains electricity costs about 5p for 250Wh in the UK, maybe a bit more in developing countries with lower population density. Best offers I can find on domestic quantities of rice at the moment are a bit under £1/kg here, even by the ton on the Indian wholesale market it only drops to about Rs2100/Qtl for the cheapest grade (called "Government Quality", which tells you all you need to know about Communism) equivalent to about 20p/kg