Where to Buy Cheap Gadgets?

Hi there!! I need some help, my sis is in Japan and I'm asking her to buy me some gadgets. She's currently staying in Yokohama so anyone who has idea where I can have her purchase cheap gadgets like tablets or iphones near that area?

I would highly appreciate the reply.
Cheers! :)

i am from Tokyo , recommend Akiabara, its in Tokyo best place to get electronics.

Is it far from Yokohama? Is its accessible through trains?
Do you have any idea regarding price difference from the normal prices on malls? lastly do they sell iphones there? Sorry too many questions! thank you for the response!! :)

yes, I think its worth to travel from Yokohama to Aikabara , might you get some prepaid phone as well.