Verb + 不起
不起 (buqǐ) is a complement that conveys inability to face or afford something, most commonly seen in 对不起 (sorry, literally "cannot face"). It attaches after a verb to indicate that the action cannot be sustained or justified, as in 买不起 (cannot afford to buy).
这个包太贵了,我买不起。
Zhège bāo tài guì le, wǒ mǎi bù qǐ.
This bag is too expensive — I can't afford it.
对不起,我迟到了。
Duìbùqǐ, wǒ chídào le.
I'm sorry, I'm late.
这么好的机会,我可不能对不起自己。
Zhème hǎo de jīhuì, wǒ kě bù néng duìbùqǐ zìjǐ.
With such a great opportunity, I can't let myself down.