Deal link: https://www.bol.com/nl/nl/p/oral-b-pro- ... 048988776/
Price: €4.95
Retailer: Bol.com

The lowest price is usually anywhere from 3.75 and 5 euros for one piece, depending on whether you live in the Netherlands or Belgium. At the Kruidvat they are now 2 + 2 free, so you have 4 for 10 euros. At bol.com you can get 3 for just under 5 euros.