When you have two ion-select items in the same ion-item. They are placed next to each other. When you place a ion-select and an ion-input item within the same ion-item they are placed below each other.
I need this because the textbox contains a price of an object and the select is the currency used.
Did you try using a grid?
Yes, but then there are no items shown at all 
You probably see nothing because you put your ion-grid inside an ion-item. Just use the ion-grid instead of the ion-item, not inside it. At least, that’s what I noticed. And either way, I have it inside an ion-list, though I don’t know if that makes a difference.