Det koster én million.

Because Norwegian, like English, normally needs a subject in a full sentence. Here det works like English it in It costs one million.

Sometimes det refers to something already understood from context, and sometimes it is just the natural subject needed for the sentence.

Koster is the present tense of å koste, which means to cost.

So:

• å koste = to cost
• koster = costs / is costing
• kostet = cost / costed

In Det koster én million, the tense is present: It costs one million.

Én is the numeral one, written with an accent to make it clear that it means the number one, not the indefinite article a/an.

So:

• en million can mean a million or one million
• én million clearly means one million

In everyday writing, many people still write en million, but én is very common when the speaker wants to emphasize the number.

Because the number is one. After one, Norwegian uses the singular noun:

• én million = one million
• to millioner = two million(s)

So million is singular here, just like English one million.

No. Det koster én million only says the amount, not the currency.

In context, the currency is usually understood. In Norway, people will often assume kroner if nothing else is specified. If you want to be explicit, you can say:

• Det koster én million kroner.

Yes, in the right context.

Use den when you are referring back to a specific common-gender noun, for example:

• Bilen? Den koster én million.
  The car? It costs one million.

Use det when referring to a neuter noun, a whole situation, or when speaking more generally. So det koster én million is a very natural general sentence.

In Norwegian main clauses, yes/no questions are usually made by putting the verb first:

• Det koster én million. = It costs one million.
• Koster det én million? = Does it cost one million?

That verb-first pattern is very common in Norwegian questions.

You normally put ikke after the verb:

• Det koster ikke én million.

That means It does not cost one million.

If you want contrast, this structure is also common:

• Det koster ikke én million, men to.
  It doesn’t cost one million, but two.

Pronunciation varies by dialect, but in a careful Eastern Norwegian pronunciation, it is roughly:

• det KOS-ter eyn mil-YOON

A few useful notes:

• koster has stress on the first syllable: KOS-ter
• én is stressed because it is the number one
• million has stress on the last syllable

In everyday speech, det is often pronounced more like de than a fully clear det.