* 昨日買ったときより更に下がってた (今は昨日より価格が下がっている)(価格が下がっている) 

In this sentence, 昨日 (last night) is used to indicate the time when the speaker bought something, and 買った (bought) is used as a past tense form of 買う (to buy). より (from) is used to indicate the time when the speaker bought something compared to the present time. 更に (even more) is used to indicate that the price of the item has decreased even further than it was yesterday. た (it) is used to indicate the direct object of the sentence, which in this case is the price of the item.

In the third sentence, でも (even though) is used to indicate that the speaker is still shocked by the price drop, even though it has decreased even further than it was yesterday. まだ (still) is used to indicate that the price drop has not been reversed or changed. ほんの (a little) is used to indicate a small or insignificant amount.

In the fourth sentence, 昨日 (last night) is used again to indicate the time when the speaker bought something, and 買った (bought) is used as a past tense form of 買う (to buy). より (from) is used to indicate the time when the speaker bought something compared to the present time. 更に (even more) is used again to indicate that the price of the item has decreased even further than it was yesterday. た (it) is used to indicate the direct object of the sentence, which in this case is the price of the item.

I hope this helps! Let me know if you have any other questions.