Simply be honest and say that you can't afford it, or offer a reduced amount toward the cost. If you don't say no to this the1bg you'll be expected to contribute to other things too.
If you offer a reduced contribution make it clear that you can't afford to pay toward anything else. If your extremely wealthy parents aren't prepared to purchase this for themselves, whose to say they'll make use of it anyway.
No need to feel guilty so don't allow anyone to make you feel that way.
ICE’s rule of terror continues in USA
Farage has resigned as an MP for Clacton?
What is the most random school memory you have?
If you are dealing with narcissism, let’s all help each other.
