Le montant dû est exact, encore que le tarif soit élevé.

French usually needs an article where English often does not. So le montant dû literally means the amount owed / the amount due.

Here:

• le = the
• montant = amount
• dû = owed / due

Leaving out le would sound incomplete in a normal sentence.

Here dû is the past participle of devoir, and it means owed or due.

So:

• le montant dû = the amount owed / the amount due

The circumflex in dû helps distinguish it from du, which is very common and usually means:

• some
• of the
• or the contraction of de + le

In modern French, accents can sometimes seem optional in certain words, but in dû the circumflex is still very useful because it prevents confusion.

Yes. In this sentence, exact means accurate or correct, not just exact in the narrow English sense.

So:

• Le montant dû est exact = The amount due is correct/accurate

French exact is often used where English would naturally say:

• correct
• accurate
• right

Encore que means something like:

• although
• even though
• though
• albeit

It introduces a concession: the first part is true, but the speaker adds a limiting or contrasting idea.

So the structure is roughly:

• The amount due is correct, although the rate/price is high.

It is a fairly formal or literary expression. In everyday spoken French, learners are more likely to hear:

• bien que
• même si
• quoique

Because encore que normally takes the subjunctive.

The verb here is être, and its subjunctive form in the third person singular is soit:

• qu’il soit
• que le tarif soit

So:

• encore que le tarif soit élevé

not:

• encore que le tarif est élevé

This is one of the key things learners notice: some conjunctions trigger the subjunctive, and encore que is one of them.

The present subjunctive of être is:

• que je sois
• que tu sois
• qu’il/elle/on soit
• que nous soyons
• que vous soyez
• qu’ils/elles soient

In your sentence, the subject is le tarif, which is third person singular, so the form is soit.

Here élevé means high.

So:

• le tarif soit élevé = the rate/price is high

French often uses élevé for things like:

• prices
• costs
• rates
• numbers
• levels

Examples:

• un prix élevé = a high price
• des frais élevés = high fees
• un taux élevé = a high rate

They are related, but they do not mean the same thing.

• montant = the total amount, the sum to be paid
• tarif = the rate, charge, pricing scale, or fee level

So the sentence suggests:

• the final amount charged is mathematically correct,
• even though the underlying rate or pricing is high.

In other words, the bill is correct, but the pricing itself is expensive.

Because the two clauses follow different grammar rules.

First clause:

• Le montant dû est exact
• This is a straightforward statement, so it uses the indicative: est

Second clause:

• encore que le tarif soit élevé
• encore que triggers the subjunctive, so it uses soit

So the change is not random; it is caused by the conjunction encore que.

Yes, it sounds fairly formal, written, or administrative.

Reasons:

• montant dû is somewhat formal/financial language
• encore que is more literary or formal than everyday spoken alternatives

A more everyday French version might be something like:

• Le montant à payer est correct, même si le tarif est élevé.
• Le montant dû est exact, bien que le tarif soit élevé.

Your original sentence is perfectly good French, but it is not especially casual.

Yes, in many contexts you could.

For example:

• Le montant dû est exact, bien que le tarif soit élevé.

That would also mean:

• The amount due is correct, although the rate is high.

Like encore que, bien que also takes the subjunctive:

• bien que le tarif soit élevé

For most learners, bien que is more common and easier to recognize than encore que.

A careful approximate pronunciation is:

Luh mohn-tahn dew ay zeg-zakt, ahn-kor kuh luh ta-reef swah ay-luh-vay.

A few useful notes:

• dû sounds like dew
• exact is pronounced roughly eg-zakt
• soit sounds like swah
• élevé sounds like ay-luh-vay

Also, in natural speech:

• est exact flows together smoothly
• encore que may sound like one rhythmic chunk

In standard French, encore que is normally followed by the subjunctive.

So learners should treat this as the normal rule:

• encore que + subjunctive

Example:

• Encore qu’il soit tard...
• Encore que ce soit vrai...

If you are still learning, the safest approach is simple: whenever you use encore que, expect the subjunctive.