This question's explanation and your answers so far.
インターネット上で通信販売を行っている A 社は，販売促進策として他社が発行するメールマガジンに自社商品 Y の広告を出すことにした。広告は，メールマガジンの購読者が広告中の URL をクリックすると，その商品ページが表示される仕組みになっている。この販売促進策の前提を表のとおりとしたとき，この販売促進策での収支がマイナスとならないようにするためには，商品 Y の販売価格は少なくとも何円以上である必要があるか。ここで，購入者による商品 Y の購入は 1 人 1 個に限定されるものとする。また，他のコストは考えないものとする。
| ① | メールマガジンの購読者数 | 100,000人 |
| ② | ①のうち，広告中の URL をクリックする割合 | 2% |
| ③ | ②のうち，商品 Y を購入する割合 | 10% |
| ④ | 商品 Y の 1 個当たりの原価 | 1,000円 |
| ⑤ | 販売促進策に掛かる費用の総額 | 200,000円 |
1,020 yen is a value that looks like a thin markup added to the cost of 1,000 yen by some other reasoning rather than allocating the 200,000-yen promotion cost per unit, and it cannot even recover the cost sufficiently. At this price, even selling 200 units gives revenue of 204,000 yen against a total cost of 400,000 yen, a large loss, so the balance is negative.
1,100 yen is a value obtained by mistakenly adding some other smaller amount, instead of adding to the cost the 1,000 yen you get by dividing the 200,000-yen promotion cost by the 200 units sold. Revenue is 1,100 × 200 = 220,000 yen, which falls short of the total cost of 400,000 yen, resulting in a loss.
1,500 yen is an intermediate value that stops partway through the calculation of cost 1,000 yen + promotion cost per unit 1,000 yen = 2,000 yen. Revenue is 1,500 × 200 = 300,000 yen, which falls below the total cost of 400,000 yen, so the balance is negative and the condition is not met.
正解 First, find the number of units sold. Of the 100,000 subscribers, 2% click the URL, and of those, 10% purchase product Y, so the number of purchasers = 100,000 × 0.02 × 0.10 = 200 people. Since each person buys one unit, the number of units sold is 200. Next, total up the costs incurred by this sales promotion. The product cost is 1,000 yen × 200 units = 200,000 yen, and adding the total promotion cost of 200,000 yen gives a total cost = 400,000 yen. The condition for the balance not to become negative (revenue ≥ expense) is: letting the selling price be P, P × 200 ≥ 400,000, so P ≥ 2,000 yen. Therefore the selling price must be at least 2,000 yen, and the correct answer is エ.