Phuket is a sizeable island with a huge variety of accommodation and beaches that have very different clientele and "feel." There is less and less available in the backpacker/hostel range on some beaches. Some beaches are definitely skewed to the upmarket crowd. How much you pay for a Phuket experience depends mostly on WHEN you go, and for most accommodations (definitely the 3-4* variety) prices in the low season may be half of what they are in the high season. I have been to Phuket many times, and except for February 2008 which was against my better judgment, I have always ventured only in the off-season (April, July, August, early October). July-September are definitely rainy season and some years, June and October can also be more wet than dry. However, in my experience, usually you get a couple of hours or so of hard afternoon rain but it is not continuous day after day 24/7--unless you get incredibly unlucky. Most beaches in rainy season will not be safe for swimming due to rips and undertows, except for a few locations at very low tide. Time to hit the pool instead. Bonus though, is that there are relatively few tourists. If you prefer to have the odds of good weather in your favor AND miss the worst of the crowds and high prices, aim for latter part March thru May (except for April Songkran holiday period). Maybe mid-October to early November. Mid-November to end of February is usually a nightmare of heaving masses.

This pricing difference between high vs low tourist season in Thailand actually holds true everywhere, not just in Phuket and the southern beach areas. The amount of the difference may be most extreme in Phuket, though. IMO, the southern tourist beach areas of Thailand are among my least favorite parts of the country--also the most unrepresentative, the most expensive, and the least friendly of natives. So if you aren't stuck on being on a beach, you might consider focusing your visit elsewhere in Thailand...such as the north or north-central. It will certainly be kinder on your budget.