Měsíční paušál je vysoký, ale signál je dobrý.

Because it is an adjective agreeing with paušál.

• paušál is masculine inanimate singular
• the sentence uses the nominative singular form, because paušál is the subject
• adjectives must match the noun in gender, number, and case

So:

• měsíční paušál = monthly plan / monthly flat rate

This adjective belongs to a soft adjective pattern, which is why it ends in -í rather than -ý.

For the same reason: both adjectives agree with masculine singular nouns in the nominative.

• paušál → masculine inanimate singular → vysoký
• signál → masculine inanimate singular → dobrý

So the structure is:

• paušál je vysoký
• signál je dobrý

If the noun changed gender, the adjective would change too:

• cena je vysoká = the price is high
• spojení je dobré = the connection is good

They are in the nominative case.

In this sentence, both nouns are the subjects of their clauses:

• Měsíční paušál je vysoký
• signál je dobrý

After je here, the adjectives vysoký and dobrý are predicate adjectives describing the subject.

In normal standard Czech, repeating je is the most natural choice here:

• Měsíční paušál je vysoký, ale signál je dobrý.

You can sometimes omit a repeated verb in Czech if the meaning is obvious, but in this sentence that would sound more elliptical or less complete:

• Měsíční paušál je vysoký, ale signál dobrý.

That is understandable, but the full version with both je forms is better for learners and more neutral.

Because Czech has no articles.

So Czech simply says:

• paušál = the plan / a plan
• signál = the signal / a signal

Whether English uses the, a, or no article at all depends on context, but Czech does not mark that with a separate word.

Paušál often means a flat-rate plan, subscription plan, or the monthly charge for that plan.

In everyday Czech, especially in telecom contexts, it can refer to:

• the mobile plan itself
• the monthly fee you pay for it

So in this sentence, měsíční paušál is something like:

• monthly plan fee
• monthly flat rate
• monthly subscription charge

Good question. Both can work, but the nuance is a little different.

• vysoký = high in amount, level, or number
• drahý = expensive / costly

So:

• Měsíční paušál je vysoký focuses on the amount being high
• Paušál je drahý means the plan is expensive overall

With prices, fees, salaries, and rates, Czech often uses vysoký very naturally.

Because ale means but, and in Czech a comma is normally used before it when it joins two clauses.

So:

• Měsíční paušál je vysoký, ale signál je dobrý.

This is standard Czech punctuation.

Yes. Czech word order is more flexible than English, although the original sentence is the most neutral.

Possible alternatives include:

• Signál je dobrý, ale měsíční paušál je vysoký.
• Měsíční paušál je vysoký, ale dobrý je signál.
  This sounds more marked or contrastive.

The original version is straightforward and neutral:

• first statement
• then contrast with ale

A rough English-friendly guide would be:

MYEH-see-chnee POW-shahl yeh VI-soh-kee, AH-leh sig-naal yeh DO-bree

A few useful points:

• ě after m gives a mye-like sound
• š sounds like sh
• č sounds like ch
• á is a long a
• ý / í are long vowel sounds

Also remember that Czech stress is usually on the first syllable of each word:

• MĚsíční
• PAUšál
• SIGnál
• DOBrý

It can mean many kinds of signal, not just mobile reception.

Depending on context, signál can refer to:

• phone signal
• radio signal
• TV signal
• a signal in a general sense

In this sentence, because of měsíční paušál, most learners will correctly understand it as mobile/network signal.

Most likely, yes.

The combination of:

• měsíční paušál = monthly plan / monthly fee
• signál = signal

strongly suggests a phone or telecom context.

So the sentence sounds like someone evaluating a provider or tariff:

• the monthly fee is high
• but the reception is good