Learn Hardcore Croatian: Ne možemo si svaki dan priuštiti skupi ručak u restoranu. - We cannot afford an expensive lunch in the restaurant every day.

si is a short (clitic) reflexive dative pronoun = “to oneself / for oneself”.
Literally, Ne možemo si priuštiti skupi ručak… is like:
“We cannot afford ourselves an expensive lunch…”

You normally need that si with this meaning.

Compare:

Ne možemo si svaki dan priuštiti skupi ručak.
= We can’t afford an expensive lunch for ourselves every day.
Ne možemo im svaki dan priuštiti skupi ručak.
= We can’t afford an expensive lunch for them every day. (im = “to them”)

So si shows that we are the ones we’re affording the lunch to.

Could I say Ne možemo se svaki dan priuštiti skupi ručak instead of si?

No, Ne možemo se priuštiti is wrong in standard Croatian.

se is reflexive in accusative/genitive, but priuštiti (nekome) nešto takes a dative object for the person:
- priuštiti nekome nešto = “to afford / grant something to someone”
The reflexive dative forms are si (short clitic) or sebi (full form).

Correct options are:

Ne možemo si svaki dan priuštiti skupi ručak…
Ne možemo sebi svaki dan priuštiti skupi ručak…

So: with priuštiti in this meaning, use si / sebi, not se.

Why is si after možemo? Could I say Ne si možemo…?

You can’t move si freely. It’s a clitic, and Croatian clitics follow fairly strict word-order rules.

In this sentence the usual pattern is:

Ne + conjugated verb + clitic(s) + the rest
Ne možemo si svaki dan priuštiti… is natural.
Ne si možemo… or Si ne možemo… are ungrammatical.

For now, a simple rule that works well in many cases:

Put ne + možemo together
Then put si right after that conjugated verb: ne možemo si …

Why isn’t the subject pronoun mi (“we”) written? Why not Mi ne možemo si…?

Croatian normally omits subject pronouns because the verb ending already shows the person and number:

možemo clearly tells you the subject is “we”.

You only add mi for emphasis or contrast:

Mi ne možemo si svaki dan priuštiti skupi ručak, ali oni mogu.
= We can’t afford it every day, but they can.

In a neutral sentence, Ne možemo si… without mi is the default, natural choice.

Why is it skupi ručak and not skup ručak?

The adjective meaning “expensive” can appear as skup or skupi before a masculine noun in the singular. Both are used in modern Croatian.

skupi ručak – very common, fully standard.
skup ručak – also possible, but skupi is more usual in this attributive position.

Grammatically, in this sentence:

skupi = masculine singular (nominative/accusative) form of the adjective
ručak = masculine singular noun

They agree in gender, number, and case, so skupi ručak is correct and natural.

What case is skupi ručak, and how can I tell?

skupi ručak is in the accusative singular, because it’s the direct object of priuštiti (“afford”).

Pattern:

tko/što? (who/what?) – nominative: (taj) skupi ručak je ukusan
koga/što? (whom/what?) – accusative: priuštiti (koga/što?) skupi ručak

With inanimate masculine nouns like ručak, nominative and accusative forms look the same:

Nominative: ručak
Accusative: ručak

So you know it’s accusative from its function in the sentence, not from a changed ending.

Why is it u restoranu, not u restoran?

Because u can take two different cases with two different meanings:

u + locative = in, inside
- u restoranu = in the restaurant
- sjedimo u restoranu – we’re sitting in the restaurant
u + accusative = into, to (movement into)
- u restoran = into the restaurant / to the restaurant
- idemo u restoran – we’re going to the restaurant

In your sentence:

You’re talking about having lunch in the restaurant, not going into it.
So you use locative: u restoranu.

What does svaki dan literally mean, and could I also say svakog dana?

svaki dan = “every day” (literally “each day” – svaki in accusative, dan in accusative)
Yes, you can also say svakog dana (genitive):
- svakog dana = also “every day / each day”

Both are common and correct here:

Ne možemo si svaki dan priuštiti…
Ne možemo si svakog dana priuštiti…

In everyday speech, svaki dan is a bit more common and neutral; svakog dana can sound very slightly more formal or stylistic, but the meaning is essentially the same.

Why is možemo conjugated, but priuštiti is in the infinitive form?

Croatian uses modal verbs much like English does:

moći = “can / to be able to”
Pattern: [moći (conjugated)] + [infinitive]

So:

Ne možemo priuštiti ≈ “We cannot afford”
- možemo – 1st person plural, present tense
- priuštiti – infinitive (“to afford”)

Croatian does not insert a word like “to” between them:

English: We cannot *afford … / We can **afford …*
Croatian: Ne možemo priuštiti… / Možemo priuštiti…

Why is svaki dan placed between si and priuštiti? Could it go somewhere else?

Yes, svaki dan (an adverbial expression of time) is fairly flexible in position. Some natural alternatives:

Ne možemo si svaki dan priuštiti skupi ručak u restoranu.
Svaki dan si ne možemo priuštiti skupi ručak u restoranu. (emphasis on “every day”)
Ne možemo si priuštiti skupi ručak u restoranu svaki dan.

All are understandable. The version you have:

Ne možemo si svaki dan priuštiti… sounds very natural and neutral, and avoids splitting ne možemo si from priuštiti too much.

What you cannot do is move si freely; it must stay in its clitic position:

✗ Ne svaki dan možemo si priuštiti… (bad position of si)
✓ Ne možemo si svaki dan priuštiti…

Does priuštiti si always mean “afford”, or can it have another nuance?

Priuštiti si is most often used like English “to afford / to allow oneself”, but it can carry a nuance of treating yourself / giving yourself something nice:

Ponekad si priuštimo odmor.
= Sometimes we allow ourselves a holiday / treat ourselves to a holiday.
Volim si vikendom priuštiti dobar doručak.
= I like to treat myself to a good breakfast on weekends.

In your sentence, it’s the usual “we can’t afford” meaning, but remember that depending on context it can also suggest “we can’t (comfortably) allow ourselves that luxury.”