interpretting よくこれだけの言い訳が出るものだ

Question

from the perspective of B先生

A「うわっ、B先生！　寝てないですよ！　ちょっと速いまばたきをしてたんです！　だから端から見ると目をつぶっていていかにも寝ているように見えますけど――」

授業中に寝ていたことを注意しにきたと勘違いした彼は物凄い勢いで言い訳をならべている。

咄嗟によくこれだけの言い訳が出るものだとある意味感心した。

i find it hard to derive a relevant meaning from "よくこれだけの言い訳が出るものだ"as a whole

At this moment, in a way, i admire how he often only makes these excuses?

thanks

Answer 1

だけ can mean "extent", "amount", as well as "only". これだけ here means "this extent" "this amount" "this much", not "only this".

Related threads:

• Shouldn't this phrase using だけのこと mean "just for that"?
• Is 足りるだけ with a negative verb idiomatic?
• What's the role of だけの in this sentence?

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よく here is not "often". よく, or よくも, can express "How dare you...!" with a blaming or ironical tone.

It's often followed by potential 「～(ら)れる」「～できる」 and exclamatory 「ね」「な(あ)」「ものだ」 etc. For example:

よくそんなことが言えるな。 How dare you say such a thing.

Related:

• 善くも as opposed to よく
• What does this conversation from a novel mean?

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The もの(だ) at the end expresses exclamation or surprise. See #1 in this post:

• The meanings of ものだ

Also related:

• Function of に and meaning of ものだ in this sentence

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You'd parse the sentence this way:

『[咄嗟]{とっさ}によくこれだけの言い訳が出るものだ』とある意味感心した。

[咄嗟]{とっさ}に "promptly" "at once" or "right away" modifies (言い訳が)出る, "excuses come out (of one's mouth)", not 感心した.