Этот телефон стоит своих денег.

Yes, стоить usually means to cost, and that is exactly why this sentence can be confusing.

In Этот телефон стоит своих денег, the verb still comes from стоить, but the whole expression стоить своих денег is an idiom meaning:

• to be worth the money
• to be worth what you pay for it

So here стоит is not just giving a price. It is evaluating whether the phone is worth what it costs.

Compare:

• Этот телефон стоит 30 тысяч рублей. = This phone costs 30,000 rubles.
• Этот телефон стоит своих денег. = This phone is worth the money.

Because стоить takes the genitive case for the thing that represents the cost or value.

So:

• стоить 100 рублей
• стоить времени
• стоить усилий
• стоить своих денег

The noun деньги is a plural-only noun in Russian, and its genitive plural form is денег.

That is why you get:

• nominative: деньги
• genitive: денег

This is very normal after стоить.

Russian often uses the reflexive possessive свой when something belongs to the subject of the sentence.

Here, the subject is этот телефон, and своих refers back to that subject in the sense of its own.

So своих денег literally feels like:

• its own money
• meaning: the money asked for it / the price it has

Using его would sound less natural here. In this fixed expression, Russian strongly prefers стоить своих денег.

Literally, it means something like of its own money or its own money's worth, but that literal wording sounds strange in English.

The natural English equivalent is:

• worth the money
• worth its price
• good value for the money

So it is best learned as a set phrase:

• стоить своих денег = to be worth the money

Grammatically, своих agrees with денег, not with телефон.

That means it matches денег in:

• case: genitive
• number: plural

So:

• денег = genitive plural
• своих = genitive plural

But in meaning, своих refers back to the subject, телефон.

This is very common in Russian: the possessive word agrees grammatically with the noun it modifies, while referring semantically to the subject.

No, that is not correct in standard Russian.

After стоить, Russian normally uses the genitive, not the accusative.

So you say:

• Этот телефон стоит денег.
• Этот телефон стоит своих денег.
• Этот телефон стоит 50 тысяч рублей.

Not:

• Этот телефон стоит деньги.

They are related, but not identical.

• стоит денег can mean costs money or sometimes is worth money / is valuable, depending on context.
• стоит своих денег specifically means is worth what you pay for it.

Compare:

• Ремонт стоит денег. = Repairs cost money.
• Этот телефон стоит своих денег. = This phone is worth the money.

So своих денег makes the idea much more specific and idiomatic.

Yes, absolutely. It is a very common phrase for many products, services, experiences, and even efforts.

Examples:

• Эта машина стоит своих денег. = This car is worth the money.
• Этот курс стоит своих денег. = This course is worth the money.
• Этот ресторан не стоит своих денег. = This restaurant is not worth the money.

So it is a useful general expression for talking about value.

You simply add не:

• Этот телефон не стоит своих денег.

This means:

• This phone is not worth the money.
• This phone isn't worth what it costs.

This negative version is also extremely common.

You might be understood, but it is much less natural than стоит своих денег.

Russian strongly prefers the idiomatic phrase:

• стоить своих денег

The version with цены is not the standard everyday expression for be worth the price.

So for natural Russian, it is best to learn and use:

• Этот телефон стоит своих денег.

Yes, Russian word order is flexible, but the neutral, most natural order here is:

• Этот телефон стоит своих денег.

You can move words around for emphasis, for example:

• Своих денег этот телефон стоит.

This sounds more emphatic, like:

• This phone really is worth the money.

But for normal learning and everyday use, stick with the standard order.

The stress is:

• Э́тот телефо́н сто́ит свои́х де́нег.

A rough pronunciation guide:

• EH-tuht tee-lee-FON STO-it sva-EEKH DYE-nyek

A few notes:

• этот starts with stress on the first syllable: Э́-
• телефон is stressed on the last syllable: -фо́н
• стоит is stressed on о́
• своих is stressed on the second syllable: -и́х
• денег is stressed on the first syllable: де́-

It is neutral and very common. You can use it in:

• everyday conversation
• reviews
• recommendations
• online comments
• spoken and written Russian

It is not slang, and it is not especially formal either. It is just a standard, natural way to talk about whether something gives good value for its price.