hurimaapuri ha benrina ippou de, hanbaitesuuryou ga takai.

フリマアプリ is short for フリーマーケットアプリ, literally flea market app.

In practice, it means an app where people buy and sell used or handmade items, like a mobile marketplace. Apps such as Mercari are often called フリマアプリ in Japanese.

• フリマ = short for フリーマーケット
• アプリ = app

So this is a very natural modern Japanese term.

は marks フリマアプリ as the topic of the sentence.

The sentence is saying something like:

• As for flea market apps, they are convenient, but...

So フリマアプリは sets up the thing being discussed, and the rest of the sentence gives two comments about it:

1. it is convenient
2. the selling fee is high

This is very common in Japanese: first introduce the topic with は, then describe it.

Here, が marks 販売手数料 as the subject of the second part: the selling fee is high.

So the structure is roughly:

• フリマアプリは = as for flea market apps
• 販売手数料が高い = the selling fee is high

A useful way to think about it is:

• は = topic
• が = subject inside the description

Japanese often uses both in one sentence. The overall topic is フリマアプリ, but within that topic, the thing being specifically described as high is 販売手数料.

Because 便利 is a na-adjective.

When a na-adjective directly modifies a noun or a noun-like expression, it usually takes な. In this sentence, 一方 behaves like a noun in the grammar pattern 〜な一方で.

So:

• 便利 = convenient
• 便利な一方で = on the one hand it is convenient, but...

Compare:

• 静かだ = is quiet
• 静かな部屋 = a quiet room
• 静かな一方で = while it is quiet / on the other hand...

If this were an i-adjective, there would be no な:

• 安い一方で = while it is cheap...

一方で means something like:

• on the other hand
• while at the same time
• although
• in contrast

It is used to show two contrasting aspects of the same thing.

So in this sentence:

• フリマアプリは便利な一方で、販売手数料が高い。
• Flea market apps are convenient, but on the other hand, the selling fees are high.

It is a slightly more formal or written way to show contrast than simply using でも or けど.

Yes, 〜一方で is a common pattern used to show contrast between two facts.

Typical forms are:

• verb dictionary form + 一方で
• verb nai-form + 一方で
• i-adjective + 一方で
• na-adjective + な + 一方で
• noun + である + 一方で in formal writing

Examples:

• 便利な一方で、不便な点もある。
  It is convenient, but there are also inconvenient aspects.
• 給料は高い一方で、仕事はきつい。
  The salary is high, but the job is tough.
• 利用者が増える一方で、問題も増えている。
  While users are increasing, problems are also increasing.

So your sentence follows the normal pattern exactly.

販売手数料 means the fee or commission charged when you sell something.

Breakdown:

• 販売 = sale / selling
• 手数料 = fee / commission / handling charge

In the context of apps, this usually means the percentage the platform takes from the seller after an item is sold.

So it is more specific than just 手数料, because 手数料 alone could refer to many kinds of fees.

This sentence is in plain style.

The final predicate is 高い, which is the plain form of the adjective. Japanese often uses plain style in:

• written explanations
• articles
• casual speech
• textbook example sentences

A more polite version would be:

• フリマアプリは便利な一方で、販売手数料が高いです。

Both are grammatically correct. The version without です sounds more neutral or written.

Yes, but the nuance would change a little.

For example:

• フリマアプリは便利だけど、販売手数料が高い。
• フリマアプリは便利だが、販売手数料が高い。

These also mean they are convenient, but the selling fees are high.

Differences:

• けど = very common and conversational
• が = somewhat formal/written
• 一方で = emphasizes two contrasting sides or aspects

So 一方で sounds a bit more analytical, like you are weighing pros and cons.

No. 高い can mean several things depending on context, including:

• high
• expensive
• costly

In 販売手数料が高い, it means the fee is high / expensive.

This is very common in Japanese:

• 値段が高い = the price is high
• 家賃が高い = the rent is high
• 手数料が高い = the fee is high

So here it refers to cost, not physical height.

The comma is natural, but it is not always required.

Japanese punctuation is often flexible, especially around linking expressions like 一方で. The comma helps make the contrast clearer and gives the reader a pause:

• フリマアプリは便利な一方で、販売手数料が高い。

Without the comma, it would still be understandable:

• フリマアプリは便利な一方で販売手数料が高い。

The version with the comma is easier to read and feels more natural in writing.

Normally, Japanese is not written with spaces between words.

The standard writing would be:

フリマアプリは便利な一方で、販売手数料が高い。

The spaces in your example were probably added only to make the sentence easier for learners to read and analyze. In real Japanese text, you would usually not see those spaces.