Squadron's prices have gotten insane. Recently they had a 25% off sale on everything, so I loaded up a cart with things I'd like and then on a whim compared prices with other vendors.
Scale Hobbyist and Hobbylinc had the items cheaper at their regular every day prices than Squadron did at 25% off. Including even a couple Squadron brand items!
Sprue Brothers can be a little pricey too, although they do have some hard to find items that others may not have.
If you are willing to wait a few weeks, Hannants in the UK has a good selection of hard to find items at good prices. Sometimes I can buy a hard to find detail item from them and have it shipped all the way across the pond for cheaper than it would be to buy it from Sprue Bothers.