Limit wydatków jest niski.

Because Polish often expresses “X of Y” with a noun followed by the genitive case.

So:

• limit = limit
• wydatków = of expenses / spending

This means limit wydatków literally works like “limit of expenses”, which is how Polish says “spending limit.”

The base form is:

• wydatek = expense
• plural: wydatki = expenses
• genitive plural: wydatków

So limit wydatków is a very normal Polish structure.

Because Polish usually uses the plural noun wydatki to mean expenses in a general sense.

English often uses an abstract noun like spending, but Polish commonly uses expenses instead.

So:

• wydatek = one expense
• wydatki = expenses
• limit wydatków = spending limit / limit on expenses

A singular form here would sound like a limit on one expense, not on spending in general.

Because niski has to agree with limit, and limit is:

• masculine
• singular
• nominative

So the adjective also becomes:

• niski = masculine singular

Compare:

• limit jest niski = the limit is low
• cena jest niska = the price is low
• oprocentowanie jest niskie = the interest rate is low

The adjective changes form to match the noun it describes.

Limit is in the nominative singular, because it is the subject of the sentence.

The basic structure is:

• Limit wydatków = subject
• jest = is
• niski = low

So this is a straightforward subject + verb + adjective sentence.

Because with adjectives after być (to be), Polish normally uses the nominative, not the instrumental.

So:

• Limit wydatków jest niski. = correct

This is different from many sentences with a noun after jest, where Polish often uses the instrumental:

• On jest nauczycielem. = He is a teacher.

But with adjectives:

• On jest wysoki. = He is tall.
• Limit jest niski. = The limit is low.

So niski stays in the nominative form.

Yes. In normal modern Polish, jest is usually kept in present-tense sentences like this.

So:

• Limit wydatków jest niski. = natural and correct

Dropping jest would sound unnatural in standard Polish.

This is different from some other Slavic languages where “is” can be omitted in the present tense.

Yes, very natural.

In Polish, niski is commonly used for things like:

• low price = niska cena
• low level = niski poziom
• low salary = niska pensja
• low limit = niski limit

A learner might wonder about mały (small), but mały limit is less natural if you specifically mean low in the sense of an allowed amount. Niski limit is the standard choice.

Yes, Polish word order is more flexible than English, although the neutral order here is:

• Limit wydatków jest niski.

Other orders are possible for emphasis, for example:

• Niski jest limit wydatków.
  This emphasizes low.

• Limit jest niski.
  This works if wydatków is already understood from context.

Even though word order can change, the original sentence is the most neutral and textbook-like version.

A rough pronunciation guide is:

• LI-mit vy-DAT-koof yest NEE-skee

A few helpful points:

• w is pronounced like English v
• y is a hard Polish vowel, not exactly like English i
• ó sounds like u
• final w in wydatków is pronounced like f, so -ków sounds like koof
• j in jest sounds like English y

Stress is usually on the second-to-last syllable of each word:

• LI-mit
• wy-DAT-ków
• jest
• NI-ski

Yes, that is possible, but the nuance is slightly different.

• limit wydatków = spending limit / limit of expenses
• limit na wydatki = limit for expenses / limit on spending

Both can be understood, but limit wydatków is very compact and natural as a general phrase. It sounds like the standard label or category name.

So for a simple statement like this, Limit wydatków jest niski is perfectly natural.