I'd assume it was import based issued that means that onions cost more.
I'm not sure the UK and France are good comparisons for onion prices as I'd assume they'd remain pretty stable since wild garlic is abundant in the UK (to an extent apparently a lot of people didn't eat it before the 80s because it was considered a weed).
@OP can you work out why this is happening? It's possible to grown onions from parts of onions so you might get away with doing that to keep a supply going for you to be able to use if it's going to last quite a while (though apparently they take 4 months to grow).
If only imported onions entered the country, the price would have been low. If I'm not mistaken, imports of onions were withheld for the reason that local harvesting usually starts in the 2nd week of December. That means local supply will flood the market and such abundance is supposed to bring the prices down. To everybody's surprise, however, the price continued to rise even at the end of December, and until now. It's almost hitting $13 a kilo.
There are various reasons cited. Again, there's the decision not to import. Another is hoarding and price manipulation. There's also the fact that it's holiday season, although the price has already been rising for months. As a matter of fact, just 6 months ago, a kilo is only around $2. But of all the reasons cited, none is convincing enough. I suspect that a few powerful people up there are benefitting from this that's why they prefer to keep it this way. And even though freshly harvested onions are coming in volumes, the price won't easily go down. Back when a kilo was worth $6, middlemen were only buying it from actual farmers at $0.50.
I'd say this is largely about the government sitting on its job. And it's probably intentional. The price has been rising for months, and I can't feel any urgency from them. The chairperson of the senate committee on agriculture just brushed the issue off saying she can live without onions. This is the same old woman who just encouraged people to reduce their consumption on rice when its price soared intolerably high.