What is the meaning of 売るほうも売るほうなら、買うほうも買うほうだ。


I found this grammar structure

N1もN1なら、N2もN2だ

My book explanation says that it means both N1&N2 are terrible.

They provide this example of usage.

子どもが子どもなら、親も親だ。

Now, there is also this sentence, which I can't translate into English, please
help.

> こんなつまらない商品を、売るほうも売るほうなら、買うほうも買うほうだ。

Also, why the を particle?

Thanks a lot.

