How much should I put it on ebay for?

It's going to sound weird but I have this quite old rare bratz doll that is going for £50.00 new on amazon... I was just wondering what I should sell it for on ebay? It is used but hardly... and all the parts are there except for this one very tiny pink band that I never needed to use.

I don't want to put it on buy it now, but I'd like to start a bid instead. So what do you think I should start the bid for? Also, the person will be paying postage (£3.75 on amazon). Not sure how much yet though!

Thank you in advance, please no rude comments.
Just thought I'd add that the one on amazon is Sasha, whereas I have Cloe. Does this matter? Everything else is the same, just a different doll. The Cloe one on amazon is unavailable so I can't see the price.
Just thought I'd add that the one on amazon is Sasha, whereas I have Cloe. Does this matter? Everything else is the same, just a different doll. The Cloe one on amazon is unavailable so I can't see the price.

You should start the bid for £25?