Negation + すぎる?
I learnt that you can use ～すぎる to say that something is "too...". For example, このカバンは高すぎます。 = This bag is too expensive.
Since すぎる is a verb, you can negate it: このカバンは高すぎません。= This bag is not too expensive.
Now my question is: What happens if you negate the adjective (or verb) that you added すぎる to? このカバンは高くなすぎます。Does it mean the same as the sentence above, it is not too expensive? Or does it mean that the bag is too 'not expensive', that is, too cheap?
Thanks for your help!
OK, so first of all, the correct conjugation of this seems to be ～なさすぎる not ～なすぎる, although ～なすぎる without the さ sometimes appears on various blogs and so on (so it might be a colloquial version - I'm not sure since this conjugation is used quite rarely).
高くない → 高くなさすぎる
As for the meaning, it does for the negative what すぎる does for the affirmative - it takes it to the extreme. So 高くなさすぎる would be "extremely not expensive", or "too not expensive" as you put it. But this is such a clunky way to say it, since you can use 安すぎる and it basically means the same thing.
In practice, it is mostly used with する and verbs that can have meaningful use cases with negative + すぎる. For example:
君は勉強しなさすぎだよ。- which basically means "You don't study at all!"
時間が足りなさすぎて何もできなかった。"I couldn't do anything since I had too little time." (lit. "I had too much lack of time")