Deze korting is maar één cent.

Deze means this here.

Dutch demonstratives depend on whether a noun is a de-word or a het-word:

• deze for singular de nouns, and for all plurals
• dit for singular het nouns

Because korting is a de-word (de korting), you say deze korting = this discount.

Korting means discount or price reduction.

It is a very common shopping word in Dutch:

• 10% korting = 10% discount
• studentenkorting = student discount

Even though it is related historically to kort (short) and korten (to shorten/reduce), in everyday Dutch you should just learn korting as the normal word for discount.

Dutch main clauses normally follow the verb-second rule: the finite verb comes in the second slot.

In this sentence:

• Deze korting = first slot
• is = second slot
• maar één cent = the rest of the sentence

So the order is completely normal Dutch word order.

No. Here maar means only or just.

So:

• maar één cent = only one cent

Dutch maar has several meanings. It can mean but, but in this sentence it does not. This is a very common use:

• Het kost maar vijf euro. = It only costs five euros.
• Ik heb maar tien minuten. = I only have ten minutes.

The accents show that één is the numeral one, not the unstressed article a/an.

Compare:

• een cent = a cent / one cent depending on context
• één cent = clearly one cent, often with emphasis

In writing, Dutch often adds the accents when the exact number matters or when the writer wants to stress it. In speech, één is also pronounced more strongly than the article een.

Because één is already determining the noun.

Dutch says:

• één cent
• twee cent
• drie euro

You do not add another article before the noun. So één cent is complete by itself.

It suggests that the discount is very small, often almost disappointingly small.

Compare:

• Deze korting is één cent. = neutral, just stating the amount
• Deze korting is maar één cent. = This discount is only one cent, with the feeling that that is not much

So maar often adds a sense of smallness, limitation, or not very impressive.

Yes. Slechts één cent also means only one cent.

The difference is mostly style:

• maar één cent = very common, natural, everyday Dutch
• slechts één cent = a bit more formal or written

Alleen één cent is usually not the best choice here. For amounts like this, maar or slechts is more idiomatic.

That is an important difference.

• een as an article is often weak and reduced, roughly like uhn
• één as the number one is stressed and pronounced clearly, roughly like ayn or ane, but with a pure Dutch long vowel

So in this sentence, één stands out clearly because it is the exact amount.

A rough English-friendly pronunciation is:

DAY-zuh KOR-ting is mahr ayn sent

A few notes:

• deze: first syllable stressed
• korting: stress on kor
• maar: long vowel, roughly mahr
• één: clearly stressed
• cent: close to English sent

A more natural Dutch rhythm would strongly emphasize één:

Deze korting is maar ÉÉN cent.