Bilet elli lira.

Because this is a nominal sentence in Turkish. In the present tense, 3rd person singular, Turkish usually does not use an overt word for is.

So:

• Bilet elli lira. = The ticket is fifty lira.

This is completely normal and complete in Turkish.

If you want to see the copula more clearly in other forms:

• Bilet elli liraydı. = The ticket was fifty lira.
• Bilet elli lira olacak. = The ticket will be fifty lira.
• Bilet elli liradır. = a more formal or definite-sounding The ticket is fifty lira.

So in your sentence, is is understood rather than spoken.

It can mean either one, depending on context.

Turkish does not have articles like English a/an and the. So bilet by itself can be:

• a ticket
• the ticket
• sometimes just ticket(s) in a general sense

In a real-life situation, Bilet elli lira will often be understood as:

• The ticket is fifty lira or
• A ticket is fifty lira

Context tells you which one is meant.

Turkish often puts the topic/thing being talked about first, and the information about it after that.

Here:

• bilet = the thing being discussed
• elli lira = what it is / its price

So:

• Bilet elli lira. = The ticket is fifty lira.

This order is the natural one for a simple statement like this.

Elli lira bilet would not normally work as a standard sentence meaning the same thing.
If you start with elli lira, you would usually need a different structure or a special context for emphasis.

In Turkish, after a number, the noun usually stays singular.

So you say:

• elli lira = fifty lira
• üç kitap = three books
• on öğrenci = ten students

Not:

• elli liralar
• üç kitaplar
• on öğrenciler

This is a very important pattern in Turkish:
number + singular noun

Because both words are in their basic dictionary form, and this sentence does not require a case ending.

In Bilet elli lira:

• bilet is the subject/topic
• elli lira is the predicate/complement

No accusative, dative, locative, etc. is needed.

Compare:

• Bilet elli lira. = The ticket is fifty lira.
• Bileti aldım. = I bought the ticket.
  Here bilet becomes bileti because it is a definite direct object.

So the lack of endings here is normal.

Yes, absolutely.

Turkish often allows very short, efficient sentences, especially in everyday speech.
This one is fully complete and natural.

It has everything needed:

• Bilet = what you are talking about
• elli lira = what you are saying about it

So even though English needs is, Turkish does not need an extra word here.

Yes. That is also correct, and it is a bit more explicit.

• Bilet elli lira. = The ticket is fifty lira.
• Biletin fiyatı elli lira. = The ticket’s price is fifty lira.

Breakdown of Biletin fiyatı:

• biletin = of the ticket / the ticket’s
• fiyatı = its price / the price

So the longer version makes the meaning more explicit, but the shorter version is very common and natural in everyday Turkish.

A simple approximate pronunciation is:

• bilet → bee-LET
• elli → el-LEE
• lira → lee-RA

A few helpful notes:

• Turkish vowels are pronounced more consistently than in English.
• The r in lira is usually a light tapped r, not a strong English r.
• Double ll in elli is written as two consonants, but for beginners it is enough to pronounce it clearly as el-lee.

A rough full pronunciation could be:

• bee-LET el-LEE lee-RA

Yes, very often.

You may hear or see:

• Bilet elli lira.
• Bilet elli TL.

Both mean the same thing: The ticket is 50 lira.

In speech, elli lira is very common and natural.
In writing, signs, menus, and advertisements, TL is also extremely common.

You can turn it into a question by using question intonation in speech or mi in standard written Turkish.

For example:

• Bilet elli lira mı? = Is the ticket fifty lira?

Here mı is the question particle.

So:

• Bilet elli lira. = statement
• Bilet elli lira mı? = question

This is a very useful pattern for beginners because it works with many noun/adjective sentences in Turkish.