Os dois preços são iguais.

Os is the masculine plural definite article, meaning the.

It matches preços, which is a masculine plural noun:

• o preço = the price
• os preços = the prices

In Portuguese, articles are often used more than in English. Here, os dois preços means the two prices or both prices, referring to two specific prices already known in the context.

Because preço is a masculine noun.

The number two changes for gender in Portuguese:

• dois for masculine nouns
• duas for feminine nouns

So:

• dois preços = two prices
• duas casas = two houses

The singular form is preço and the plural is preços.

The -s makes it plural, just like in many other Portuguese nouns.

The ç is there to keep the s sound before o:

• preço sounds roughly like PRESS-o
• if it were written preco, the c would sound like k

So ç is a spelling feature that preserves pronunciation.

Because the subject is plural: os dois preços.

The verb ser must agree with the subject:

• é = is
• são = are

Compare:

• O preço é igual. = The price is equal / The price is the same.
• Os dois preços são iguais. = The two prices are equal / The two prices are the same.

Because iguais is plural.

The adjective igual changes for number:

• igual = singular
• iguais = plural

So:

• O preço é igual.
• Os preços são iguais.

Unlike many Portuguese adjectives, igual does not change for masculine vs. feminine in the singular:

• o preço igual
• a tarifa igual

But in the plural, it becomes iguais for both:

• os preços iguais
• as tarifas iguais

Here, iguais means equal or the same.

With prices, it usually means the amounts match:

• both prices have the same value

In English, you might translate it as:

• The two prices are equal.
• The two prices are the same.

Yes, you could, but the nuance is slightly different.

• Os preços são iguais emphasizes that the prices are equal in value.
• Os preços são os mesmos means the prices are the same ones or the prices are the same, often with a stronger idea of exact identity or no change.

In many everyday situations, both are natural. But iguais is a very straightforward choice when talking about equal amounts.

That is the normal order in Portuguese: article + number + noun

So:

• os dois preços
• as três casas
• os quatro livros

This is the standard and natural pattern.
English speakers sometimes want to focus only on the noun first, but in Portuguese os dois preços is the normal way to say the two prices.

Grammatically, it is possible, but it changes the feel.

• Os dois preços são iguais sounds specific: the two prices
• Dois preços são iguais sounds less specific, more like two prices are equal

In most normal contexts, if you mean two particular prices being compared, os dois preços is the more natural choice.

Yes. Ambos os preços means both prices.

So:

• Os dois preços são iguais.
• Ambos os preços são iguais.

Both are correct.
Ambos is a bit more formal or more deliberate, while os dois is very common and natural in everyday speech.

A rough pronunciation is:

ooz DOYSS PREH-soos sow ee-GWYESS

A few notes:

• os often sounds like ooz in connected speech
• dois rhymes roughly with voice (but shorter)
• preços has the stress on the first syllable: PREH-ços
• são is nasal; it does not sound exactly like English sow
• iguais sounds roughly like ee-GWYESS

A more IPA-style version is approximately: [uz dojs ˈpɾesus sɐ̃w iˈgwajs]

The article and the number two would change.

For example, with tarifas:

• As duas tarifas são iguais.

Changes:

• os → as
• dois → duas

But:

• são stays the same because the subject is still plural
• iguais stays the same because it is already the plural form used for both masculine and feminine

Yes, it is completely natural.

It is a simple, standard sentence that a Brazilian Portuguese speaker could easily say in real life, especially when comparing:

• prices
• costs
• values
• tickets
• products

For example, in a store or while shopping online, this would sound normal and clear.