Imerovigli has the best overall caldera and sunset views because it has the highest elevation over the sea. That said, there are only a small handful of shops and restaurants there. Oia is the most beautiful and romantic village on the island and there are an abundance of shops, restaurants, cafes and galleries there but it also gets very busy in July because of its popularity. Yes, the top hotels are very expensive in Oia but where you choose to stay will depend on what you want for that $400. "Luxury" means different things to different people. If a full-service hotel that offers privacy and a sense of exclusivity is what you're after, and you've found that in Imerovigli, you should probably go ahead and book it. $400 won't give you that in Oia. But if you want something more traditonal and self-catering, and you want to stay in Oia, check Olympic Villas, Old Oia Houses, Rimida Villas, Strogili Houses, Nikos Villas, Majestic View Studio, Golden Sunset Villas, Lucky Homes and Zoe Aegeas Houses. Some of these have pools, some don't. There's a very nice public access pool in Oia that's free if you buy food and/or drinks. It's a great place to sit and watch the sunset away from all the hordes of lookie-loos. http://www.lioyerma.gr