Phi Phi is one of the newly-found Thai destinations for backpackers: for people coming on a budget, a lot of simple accommodation is on offer -- from guest houses to very simple backpacker dormitory rooms. See examples here.
In the high season when prices for cheap guesthouses and hotel rooms start to climb for the Christmas, New Year, Chinese New Year, Thai New year peak, it might be a little bit expensive, but especially in the Green Season very good offers can be had.
Even though it might be rain more than in high season, long stretches with many days of sunshine only can still be had, for example in early August.
Backpackers on Phi Phi Island Before "The Beach", the first backpackers arrived on Phi Phi Island from Phuket, Krabi and Samui in the middle 1980s. The main pull to the island still is the scenery and diving. A few dive schools opened up and greater numbers of travelers came.
Traveling to Phi Phi Island on a budget Traveling to Phi Phi Island has been immensely popular in the last 20 years but it has not always been like that. While backpackers were exploring the larger islands of Phuket and Koh Samui, the more remote destinations of Phi Phi, Taru Tao and Koh Mook, were relatively hidden and stayed very much untouched.