Almost doubled in 5 months Price

You will find that I ordered late on December 13 two pairs of headphones of this type, at 8.87 euros each.
They had what they had, about three months for daily use, without war thunders in sound reproduction. Just good at listening to podcasts etc.
I want to reacquire two pairs, they went to 15.02.
How to explain such increases? Nothing has increased in 5 months ... Fortunately, we'd all be on the street, you first.