Перевод - Итальянский-Английский - non riesco a capire come si fa a chiedere 40 euro...

The first line should be:
"I can't understand how someone can ask for 400€. If the price gets reasonable,..........)

Hi imreglsu43,

I don't understand what you think can be improved since your version is exactly the same the translator wrote, except for a period that is not in the original

CC: imreglsu43

Hi, messages about a translation must be posted under the translation.

imreglsu43 wrote to my inbox:

The main problem is that you left out the "for"
Also, "I don't understand" sounds better to my ear than "I can't understand"... Also, the first sentence ends after "FOR 400 €"

I'd write:
I DON'T understand how someone can ask FOR 400 €. If the price gets reasonable, we can talk again about it. I am from Vicenza.


Actually, the "for" you think was left out should be placed after the price if we had the object, but we don't.
Ex: "I can't understand how someone can ask 400 € for (sth)"
About the period, well, yes it's possible and perhaps more suitable to use it instead of the comma. We can edit that