Što se tiče pretplate, ovaj tarifni paket je skup.

Yes. Što se tiče is a very common fixed expression meaning as for, regarding, when it comes to, or in terms of.

Literally, it is built from:

• što = what/which
• se tiče = concerns / touches

But in real usage, you should learn što se tiče as a whole phrase.

Examples:

• Što se tiče posla, sve je u redu. = As for work, everything is fine.
• Što se tiče cene, preskupo je. = As for the price, it’s too expensive.

In your sentence, Što se tiče pretplate means As for the subscription or Regarding the subscription.

Because što se tiče normally takes the genitive case.

The base form is:

• pretplata = subscription

The genitive singular is:

• pretplate

So:

• što se tiče pretplate = regarding the subscription

This is something worth memorizing:

• što se tiče + genitive

More examples:

• što se tiče vremena = regarding the time/weather
• što se tiče novca = regarding money
• što se tiče mene = as for me

Not exactly, although learners often connect the two.

In this expression, što se tiče is the standard fixed form. You should learn and use it that way.

A native speaker may use šta in other contexts as what?, for example:

• Šta radiš? = What are you doing?

But in this phrase, the usual expression is:

• što se tiče

So for learners, the safest rule is:

• use šta for ordinary what?
• memorize što se tiče as one set phrase

Because Što se tiče pretplate is an introductory phrase at the beginning of the sentence.

English does the same thing very often:

• As for the subscription, this plan is expensive.

So the comma marks a short fronted topic phrase before the main clause:

• Što se tiče pretplate, = topic/introduction
• ovaj tarifni paket je skup. = main statement

Ovaj means this.

It agrees with the noun paket in:

• gender: masculine
• number: singular
• case: nominative

So:

• ovaj paket = this package/plan

Because tarifni paket is masculine singular, the demonstrative must also be masculine singular:

• ovaj tarifni paket

If the noun were feminine, you would use ova:

• ova pretplata = this subscription

If it were neuter, you would use ovo:

• ovo selo = this village

Because paket is a masculine noun, and adjectives must agree with the noun they describe.

So:

• tarifni = masculine singular nominative
• paket = masculine singular nominative

That is why you get:

• ovaj tarifni paket

Compare:

• tarifni paket = masculine
• tarifna opcija = feminine
• tarifno rešenje = neuter

Serbian adjectives always change form to match the noun.

Because skup must agree with paket, which is masculine singular.

So:

• paket = masculine singular
• skup = masculine singular adjective meaning expensive

Compare:

• Ovaj paket je skup. = masculine
• Ova pretplata je skupa. = feminine
• Ovo rešenje je skupo. = neuter

This is a very important pattern in Serbian: the adjective after to be still agrees with the noun.

It can mean more than one thing depending on context.

Most commonly:

• skup = expensive

But in other contexts, skup can also mean:

• gathering
• set/collection
• part of words related to assembling or collecting

In your sentence, because it describes a pricing plan, it clearly means:

• expensive

So:

• ovaj tarifni paket je skup = this tariff plan is expensive

It usually means subscription or subscription service/arrangement.

Depending on context, it can refer to:

• the act of subscribing
• a subscription contract
• a recurring payment
• in telecom contexts, something close to subscription plan or monthly service

Meanwhile, tarifni paket is more specifically the tariff plan / pricing package.

So the sentence separates two ideas:

• pretplata = the subscription side of things
• tarifni paket = the actual plan/package

That is why the sentence sounds like:

• As far as the subscription is concerned, this tariff plan is expensive.

Serbian often uses noun phrases where English might use a single everyday word like plan.

In telecom language:

• tarifni paket = tariff package / plan
• paket by itself can also be used if the context is clear

So in real life, speakers may say:

• Ovaj paket je skup. = This plan is expensive.

The longer phrase tarifni paket is a bit more explicit and formal.

Yes. Serbian word order is more flexible than English, although not completely free.

The sentence as given is very natural:

• Što se tiče pretplate, ovaj tarifni paket je skup.

But other versions are possible, depending on emphasis:

• Ovaj tarifni paket je, što se tiče pretplate, skup.
• Ovaj tarifni paket je skup, što se tiče pretplate.
  This last one is less neutral and may sound more marked or conversational.

For learners, the safest and most natural version is the original:

• topic phrase first
• then the main clause

Yes, if the context already makes it clear that you are talking about phone or service plans.

• ovaj paket je skup = this package/plan is expensive

Adding tarifni makes it more precise:

• ovaj tarifni paket je skup

So:

• with context: shorter version is fine
• without context: longer version is clearer

It is mostly neutral to slightly formal.

Why:

• što se tiče is a standard, common phrase
• tarifni paket sounds a bit technical or official
• the whole sentence sounds natural in written language, customer service, reviews, and everyday discussion

A more casual speaker might shorten it:

• Što se tiče pretplate, ovaj paket je skup.

So the original sentence is perfectly normal, just a little more precise than everyday casual speech.

It breaks down into two parts:

1. Što se tiče pretplate,

   • introductory topic phrase
   • literally something like as concerns the subscription
   • idiomatically as for the subscription / regarding the subscription

2. ovaj tarifni paket je skup

   • ovaj tarifni paket = subject
   • je = is
   • skup = adjective/predicate adjective

So the structure is:

• Topic phrase + main clause
• Regarding X, Y is expensive

That pattern is very common in Serbian.