Learn Hardcore French: Le timbre ne coûte pas cher, et la poste est près de la mairie. - The stamp is not expensive, and the post office is near the town hall.

In spoken French, people very often drop ne and just say:
Le timbre coûte pas cher.
This is informal but extremely common.
In writing and in careful speech, you should keep both ne and pas.

Why does French say coûter cher instead of something like coûter beaucoup?

The verb coûter (to cost) often combines with cher to mean to be expensive.

coûter cher = to be expensive / to cost a lot
ne pas coûter cher = not to be expensive / not to cost much

So Le timbre ne coûte pas cher is the natural French way to say that the stamp is not expensive.
You would not normally say coûter beaucoup to mean be expensive; that sounds odd or incomplete by itself. You can say things like:

coûter beaucoup d’argent = to cost a lot of money

but when you just want expensive / not expensive, you use cher with coûter.

Should cher agree with timbre? Why is it not chers or chère?

After coûter, cher behaves like an adverb, not an adjective. As an adverb, it is invariable: it does not change form for gender or number.

So you say:

Le timbre coûte cher.
Les timbres coûtent cher.
Cette robe coûte cher.
Ces robes coûtent cher.

In all cases, cher stays the same.

If you use être instead of coûter, then cher is an adjective and it must agree:

Le timbre est cher.
Les timbres sont chers.
Cette robe est chère.
Ces robes sont chères.

So:

Les timbres ne coûtent pas cher. ✅
Les timbres ne coûtent pas chers. ❌

Can I say Le timbre n’est pas cher instead of Le timbre ne coûte pas cher?

Yes, you can. Both are correct and common.

Le timbre ne coûte pas cher.
Le timbre n’est pas cher.

They both mean that the stamp is not expensive. The nuance is small:

coûter cher / ne pas coûter cher focuses slightly more on the idea of price / cost.
être cher / n’être pas cher is more like simply is expensive / is not expensive as a quality.

In everyday speech, both forms are used a lot; you can treat them as practically interchangeable.

Just remember: with être, cher is an adjective and agrees:

Les timbres ne sont pas chers.

Could I say Le timbre est bon marché instead of ne coûte pas cher?

Yes.

Le timbre est bon marché. = The stamp is cheap / good value.
Le timbre ne coûte pas cher. = The stamp is not expensive.

Both are natural. Note:

bon marché is an idiomatic expression meaning cheap / inexpensive.
bon marché is also invariable: it does not change for gender or number.

So you say:

Cette robe est bon marché.
Ces robes sont bon marché.

Never bons marchés or bonnes marchés.

Why is it le timbre and not un timbre or just timbre?

The definite article le can have several uses here:

Generic meaning: talking about a thing in general.
French often uses a definite article where English uses no article:
- Le timbre ne coûte pas cher.
  can mean Stamps are not expensive (in general), depending on context.
Context‑specific stamp: a stamp already known in the conversation.
For example:
- You are at the post office, pointing at the stamp you need.
  Le timbre ne coûte pas cher = That stamp (the one we’re talking about) is not expensive.

Other options:

Un timbre ne coûte pas cher.
This sounds like a stamp is not expensive (a bit more generic, like any one stamp).
Timbre ne coûte pas cher.
Without an article is incorrect in standard French for a common noun.

So you generally need an article, and le is very natural when talking about a typical or specific stamp.

What exactly does la poste mean here? Is it the same as post office?

In this sentence, la poste refers to the postal service or, in everyday language, the post office.

French speakers often say la poste as a shortcut for le bureau de poste (the post office building):

Je vais à la poste. = I am going to the post office.

More precisely:

la poste can mean the postal service as an institution.
le bureau de poste is the actual office or branch.

In practice, Je vais à la poste is the standard everyday way to say I am going to the post office.

What is the difference between la poste and le poste?

They are completely different words:

la poste (feminine)
- the postal service, and by extension the post office.
- Example: La poste est près de la mairie.
le poste (masculine)
has several meanings depending on context:
- a job, position: un poste de professeur
- a station: un poste de police (a police station)
- a set: un poste de télévision (a TV set), un poste de radio

So:

Je vais à la poste. = I am going to the post office.
Je vais au poste de police. = I am going to the police station.

How does près de work? Why do we need de after près?

When près is followed by a noun, it must be used with de:

près de
- noun

In this sentence:

près de la mairie = near the town hall

Other examples:

près de la gare = near the station
près du parc = near the park
près de l’école = near the school
près des montagnes = near the mountains

So you cannot say près la mairie; you must say près de la mairie.

Why is it près de la mairie and not près du mairie or just près la mairie?

Two important rules are at work:

près needs de before a noun
- You must say près de
  - noun, not près
    - noun alone.
      So près la mairie is incorrect.
The choice between du / de la / de l’ / des depends on the noun’s gender and number:
- masculine singular: du (de + le)
  - près du parc
- feminine singular: de la
  - près de la mairie
- singular before vowel or silent h: de l’
  - près de l’église
- plural: des (de + les)
  - près des magasins

mairie is feminine singular (la mairie), so you must say:

près de la mairie

What exactly is la mairie? Is it the same as town hall or city hall?

La mairie is:

the town hall / city hall building
and, by extension, the municipal administration, the local mayor’s office

So près de la mairie means near the town hall.

A related word is l’hôtel de ville:

In many towns and cities, la mairie and l’hôtel de ville refer to the same place (the town hall).
mairie is more general and is also used in small towns or villages.
hôtel de ville is often used for larger or more official buildings, especially in cities.

In everyday speech, mairie is very common.

How do you pronounce Le timbre ne coûte pas cher, et la poste est près de la mairie? Any silent letters or liaisons?

Approximate pronunciation (standard French):

Le timbre → [lə tɛ̃bʁ]
- final -re in timbre is not pronounced as a full syllable; you mainly hear the bʁ at the end.
ne coûte pas → [nə kut pa]
- final -e in ne is very light; in casual speech, ne often disappears: [kut pa].
- final -t in coûte is pronounced because it is followed by a vowel (pas)?
  Actually no: coûte [kut] is closed; the t is pronounced regardless, but there is no liaison with pas.
cher → [ʃɛʁ]
- final -r is pronounced in standard French.
et la poste → [e la pɔst]
- the e in et is open [e].
- final -e in poste is silent.
est près de la mairie → [ɛ pʁɛ də la mɛʁi]
- est is [ɛ], and there is no liaison before près.
- près ends in a pronounced -s sound [pʁɛs].
- de is [də] (schwa); in fast speech it can be very reduced.
- mairie is [mɛʁi]; both syllables clearly pronounced.

In very natural, informal speech, the whole sentence might sound closer to:

Le timbre coûte pas cher, la poste est près d’la mairie.
with ne dropped and de la reduced in pronunciation.