Well, you can always make the same request to match the highest bid for urself if you feel imba, perhaps u can asked for something equivalent to a laptop as well? Lol.

In my perception, if you are a student, I think u should really reconsider this kinda outing.

If you are working adult earning decent income; I think it's fine though. Perhaps u can propose to set a budget for everyone and revisable every year or something ?

Eg;
2016 - budget for each bday rm 100/pax. Min, if wan chip more; sendiri decided