On a budget, Museum of Prehistoric Thera still earns its price.
~€6 (or combined ticket)
The essential complement to Akrotiri: small, air-conditioned, and home to the wall paintings and artifacts that bring the buried town to life. The catch is that it's modest in scale and means little without context — pair it with the dig site. For history-minded travelers it's an hour very well spent; others will breeze through.