Festpreis und Verkaufspreis sind fair.

Because the subject has two nouns: Festpreis und Verkaufspreis. In German, two singular nouns joined by und normally take a plural verb.

• Der Festpreis ist fair.
• Der Verkaufspreis ist fair.
• Festpreis und Verkaufspreis sind fair.

So each noun is singular, but together they form a plural subject.

In German, all nouns are capitalized. Both Festpreis and Verkaufspreis are nouns, so they begin with capital letters.

By contrast, fair is an adjective here, so it is not capitalized.

German can sometimes leave out articles when speaking in a general, category-like, or somewhat headline/business-style way.

So Festpreis und Verkaufspreis sind fair can sound more general or concise.

If you want to refer to specific prices in a more fully marked way, you can also say:

• Der Festpreis und der Verkaufspreis sind fair.

That version sounds more clearly like the fixed price and the selling price in a particular situation.

Yes. Both are compound nouns, which are very common in German.

• Festpreis = fest
  • Preis
• Verkaufspreis = Verkauf
  • Preis

In German compounds, the last part is the main noun. Here that last part is Preis, so both words are kinds of price.

This is why both words behave grammatically like Preis.

That -s- is a linking element, often called a Fugen-s in German grammar.

So:

• Verkauf
  • s
    • Preis = Verkaufspreis

It does not usually have a separate meaning by itself. It is just a very common way German joins parts of compound words.

Because fair is a predicate adjective here, used after the verb sein. Predicate adjectives in German normally do not take adjective endings.

So you say:

• Der Preis ist fair.
• Die Preise sind fair.

But when the adjective comes before a noun, it does take an ending:

• ein fairer Preis
• faire Preise

So:

• Die Preise sind fair ✅
• die fairen Preise ✅
• Die Preise sind faire ❌

Yes. Fair is a very common German adjective borrowed from English, and it is fully normal in everyday German.

It is often used for things like:

• faire Preise = fair/reasonable prices
• faire Bedingungen = fair conditions
• fair handeln = to act fairly

For prices, fair usually means something like reasonable, not excessive, or justifiable.

Both are masculine, because the final part Preis is masculine.

• der Festpreis → plural die Festpreise
• der Verkaufspreis → plural die Verkaufspreise

In the sentence, the words themselves are still singular nouns, but because there are two of them together, the verb is plural: sind.

This follows normal German main-clause word order. In a simple statement, German usually puts the finite verb in second position.

Here the first position is taken by the whole subject:

• Festpreis und Verkaufspreis = position 1
• sind = position 2
• fair = rest of the sentence

So the structure is:

Subject + verb + predicate adjective

This is very typical in German:

• Der Preis ist hoch.
• Das Angebot ist gut.
• Festpreis und Verkaufspreis sind fair.