The Xperia XA2 Plus seems to be a product wich is only sold by exclusive retailers.

In Germany it's sold by Saturn and MediaMarkt wich are in fact both the same retailer.

Here are some links:
Belgium:
official productpage

Germany:
official productpage - Saturn - MediaMarkt (369 EUR)

France:
official productpage
sony store (369 EUR)

Spain:
official productpage - Amazon (399,90 EUR)

Italy:
official productpage - sony store (369 EUR)

Netherlands:
official productpage

Poland:
official productpage - various dealer (1.699 PLN ~ 395 EUR)

Portugal:
official productpage

Russia:
official productpage - various dealer (2.5990 RUB ~ 343 EUR)

Switzerland:
official productpage (de) - official productpage (fr)

Austria:
product page

Except for eastern europe there seems to be no competition at all so the prices will most likely remain stable.

For Belarus, Czech Republic, Denmark, Greece, Ireland, Hungary, Norway, Romania, Finland, Sweden, Turkey, UK and Ukraine there are even no official informations available at all.