D’après le devis, le montant est élevé.

Here d’après means according to or based on.

So:

• D’après le devis = According to the quote/estimate

It is a fixed expression. You can use it before a noun or pronoun:

• D’après Marie, c’est vrai. = According to Marie, it’s true.
• D’après ce document, il faut payer demain. = According to this document, you have to pay tomorrow.

In your sentence, it introduces the source of the information: the quote/estimate.

Un devis usually means a quote, estimate, or cost estimate, especially in business, repair, construction, or services.

For example, if a company tells you how much some work will cost before doing it, that document is often un devis.

Common related idea:

• demander un devis = to ask for a quote/estimate

So le devis here is probably the document showing the expected price.

French uses articles much more often than English does.

So where English might say:

• According to the quote, the amount is high

French naturally says:

• D’après le devis, le montant est élevé.

Both devis and montant normally need an article here.

A learner might want to say something like D’après devis or montant est élevé, but that would sound incomplete or incorrect in standard French.

Le montant means the amount, usually an amount of money.

So in this sentence, it refers to the price or total sum shown on the estimate.

Examples:

• Le montant total est de 500 euros. = The total amount is 500 euros.
• Quel est le montant de la facture ? = What is the amount of the bill?

It is a slightly formal or administrative word, very common in financial contexts.

French often uses élevé to mean high when talking about prices, amounts, costs, rates, and similar things.

So:

• Le montant est élevé = The amount is high.

This is very natural French.

You may also see:

• Le prix est élevé. = The price is high.
• Les frais sont élevés. = The fees are high.

Even though élevé literally relates to something being raised or elevated, in this context it is the normal adjective for a high amount or cost.

Because élevé agrees with le montant, and montant is masculine singular.

Agreement works like this:

• masculine singular: élevé
• feminine singular: élevée
• masculine plural: élevés
• feminine plural: élevées

Examples:

• Le montant est élevé.
• La somme est élevée.
• Les montants sont élevés.
• Les sommes sont élevées.

So the ending depends on the noun being described.

Usually, no—not in this context.

For prices, amounts, costs, salaries, rates, etc., French normally uses élevé, not haut.

Natural:

• Le prix est élevé.
• Le montant est élevé.

Less natural or incorrect in standard usage:

• Le montant est haut.

Haut is more for physical height or position:

• Le mur est haut. = The wall is tall/high.
• La montagne est haute. = The mountain is high.

So for money-related amounts, élevé is the better choice.

Yes, often it can.

You could say:

• Selon le devis, le montant est élevé.

This means almost the same thing: According to the quote, the amount is high.

In many contexts, d’après and selon are interchangeable.
A slight nuance is that selon can sound a bit more formal or neutral, while d’après can feel a little more like judging from or based on what is stated in.

But in this sentence, both are fine.

The comma separates the introductory phrase from the main clause:

• D’après le devis, = introductory element
• le montant est élevé. = main statement

This is similar to English punctuation in a sentence like:

• According to the quote, the amount is high.

The comma helps readability. In some short French sentences, punctuation can vary a little, but here the comma is very natural.

A simple pronunciation guide is:

Da-pray luh duh-vee, luh mon-tan nay zay-luh-vay.

A few useful points:

• d’après sounds roughly like da-pray
• devis sounds like duh-vee
• In montant est, the final t of montant links to the following vowel. This is called liaison, so it sounds a bit like mon-tan-tay
• élevé sounds like ay-luh-vay

A more IPA-style version is:

/dapʁɛ lə dəvi, lə mɔ̃tɑ̃ ne.elve/

It sounds neutral to somewhat formal, mainly because of the words devis and montant.

This is the kind of sentence you might see or hear in:

• business communication
• customer service
• invoices or estimates
• administrative contexts

In casual everyday speech, people might sometimes say something simpler, like:

• D’après le devis, c’est cher. = According to the quote, it’s expensive.

But D’après le devis, le montant est élevé. is perfectly natural and clear in a professional context.

Yes. That is also correct, but the structure is a little different.

• D’après le devis, le montant est élevé.
  = According to the quote, the amount is high.

• Le montant du devis est élevé.
  = The amount of the quote is high.

The first version emphasizes the quote as the source of the information.
The second version directly identifies which amount you are talking about: the amount of the quote.

Both are natural, but they are not exactly the same in focus.