I doubt the seller has really tested the phones (no batteries in 70 phones, starting a phone consumes power a lot, charging takes time). I also sent the list of things which should have been tested before saying they all work (screen, slider, battery charge, usb port, speakers and audio plug, sim detection and cellular data etc.)

I also said that if they are not really tested to work the price can be 10€ because it is then spare parts only and they can't claim them to work. I hope they listen to reason.