Cheapest rice I can easily get here in the UK, equivalent to ~1600JPY/5kg: https://www.tesco.com/groceries/en-GB/products/314300009

Cheapest rice I am actually willing to eat, ~3000JPY/5kg: https://www.tesco.com/groceries/en-GB/products/293247162

Shortgrain rice, such as Japanese rice, tends to be even more expensive than that.

That said, no idea where whatever it is the article is quoting the price of falls on that scale.