Ideally, I don't advise people to spend any time less than 5 days (4 nights) on the island because it's really not worth it and you don't get to experience and appreciate what Santorini has to offer (…and there is a lot!).
How much should I budget for a trip to Santorini?
On average, a trip to Santorini will cost around $1,500-$2,000 per person for a week-long stay. This includes flights, accommodation, food, and activities. However, the cost can vary depending on the time of year you visit, the type of accommodation you choose, and the activities you participate in.