tanmatudaikin ha takai.

It is read:

たんまつだいきん は たかい。

• 端末 = たんまつ
• 代金 = だいきん
• 高い = たかい

In normal Japanese writing, you would usually write it without spaces:

端末代金は高い。

端末代金 means the price/cost of the device/terminal.

A few notes:

• 端末 literally means a terminal or device
• In everyday situations, it often refers to things like a phone, mobile device, or other electronic unit
• 代金 means price, charge, or amount to be paid

So 端末代金 is a fairly formal or business-like way to say the device cost or the price of the handset/device.

は marks the topic of the sentence.

So in:

端末代金は高い。

the topic is 端末代金. The sentence is saying something about the device cost:

• As for the device cost, it is high
• more naturally in English: The device cost is high

This is a very common Japanese pattern:

X は Y

= As for X, it is Y

Yes, 端末代金が高い is possible, but the nuance changes.

• 端末代金は高い。
  Topic-focused. It sounds like speaking of the device cost, it’s high. This is often used when the cost is already part of the conversation or when you are contrasting it with something else.

• 端末代金が高い。
  Subject-focused. This can sound more like the thing that is high is the device cost, or it may present the information more directly.

In many everyday contexts, は is the more natural choice if the speaker is making a general comment.

Because this sentence is in plain style.

• 端末代金は高い。 = plain / casual / dictionary-style
• 端末代金は高いです。 = polite

Japanese often leaves off です in plain statements, especially in:

• casual speech
• written notes
• headlines
• examples in textbooks

So the sentence is complete even without です.

Yes. 高い is an い-adjective.

In Japanese, い-adjectives can end a sentence by themselves:

• 高い。 = is expensive / is high
• 安い。 = is cheap
• 大きい。 = is big

So:

端末代金は高い。

is grammatically complete. You do not need a verb like is in English.

That is different from English, where you need is:

• The device cost is high

But in Japanese, 高い already carries the predicate function.

Here, 高い means expensive.

The adjective 高い can mean both:

• high in height/level
• expensive in price

Because the topic is 端末代金 (device cost), the meaning is naturally expensive.

So in this sentence, you should understand it as:

• The device cost is expensive
• more natural English: The device cost is high or The device is expensive

The spaces are just for learning clarity.

Normally, Japanese is written without spaces:

端末代金は高い。

Textbooks and beginner materials often add spaces to help learners see the parts:

• 端末代金
• は
• 高い

But in natural Japanese writing, those spaces are usually not used.

It is a compound noun made from smaller parts:

• 端末 = device / terminal
• 代金 = price / payment amount

Together:

• 端末代金 = device price / handset cost

Japanese often combines nouns this way to make compact expressions. English usually uses of or noun modifiers instead:

• the price of the device
• device cost

Yes, it is natural, especially in contexts like:

• phone contracts
• electronics sales
• billing explanations
• comparison charts
• customer service talk

It sounds a little business-like or matter-of-fact. In very casual conversation, someone might instead say:

• このスマホ、高い。 = This phone is expensive.
• 端末の値段は高い。 = The price of the device is high.

So 端末代金は高い。 is natural, but it has a somewhat formal or technical feel.

Yes, absolutely.

• 端末代金は高い。
• 端末の代金は高い。

Both are understandable and natural.

The difference is mainly style:

• 端末代金 is a compact compound noun, a bit more formal or business-like
• 端末の代金 is slightly more explicitly structured and may feel easier for learners to parse

Japanese often has both options:

• compound noun style
• A の B style

Both can work depending on tone and context.