I booked a room at Hotel Sol in Ollantaytambo, they helped me getting the tickets for 30 soles per ticket. I guess that's more than 10%. I am a bit desperate as I am using my isic card disc and wanting to buy the Huayna Picchu ticket too. Does anyone know if they check the card at the Machu Picchu entrance? I just want to make sure I carry the card with me.