I just started learning chinese and I came across this dialogue from a lesson:
A: Pínɡuǒzěnme mài ? 苹果怎么卖? How much are the apples?
B: Sìkuài. 四块. 4 Yuan.
A: Yǒudiǎnr ɡuì. Kěyǐpiányi yìdiǎnr mɑ? 有点儿贵。可以便宜一点儿吗？ A bit expensive. Can you make it cheaper?
B: Sān kuài wǔ. 三块五. 3,5 Yuan.
A: Zài piányi yìdiǎnr, hǎo mɑ? 再便宜一点儿，好吗？ Can you make it cheaper?
B: Hǎo, sān kuài. 好，三块。Ok, 3 Yuan.
I'm wondering about the differences between:
Kěyǐpiányi yìdiǎnr mɑ? 可以便宜一点儿吗？
Zài piányi yìdiǎnr, hǎo mɑ? 再便宜一点儿，好吗？
In the lesson they said 再 zài can mean more in chinese, so I understand literally 2. as More cheap a little bit, ok?. So it is clear the speaker wants the product to be cheaper than it is now. However I do not completely understand 1., as literally would mean Can it be cheap a little bit?, missing the comparison specifier.
Question: What's the underlying grammar structure in 1.? Does actually have the word 再 zài implicit, like
Kěyǐ(zài)piányi yìdiǎnr mɑ? 可以(再)便宜一点儿吗？
so it really becomes a "comparison" question such as 2.? Or does this mean comparisons in chinese are a little bit more flexible than other languages (like English), where you always need to specify them in some way?
I asked a chinese friend about this and he said usually 1. can be asked just single time and then if you want to ask for still a cheaper product you use 2. any number of times. Does this mean they are not completely equivalent as I expected?