It's hit or miss really weather wise. July will most likely be warmer than August, as the temps start getting cooler again in august. We went to Sitka for the 4th of July this year and it was in the low 50s and rain. In anchorage we had a warmer than usual summer with temps in the 70s, and then we had a first early snow in September with some termination dust (snow on the mountains) in late august. The kids go back to school in early-mid August. Prices may be cheaper because it's towards the end of tourist season and kids are back in school.
Be aware that excursions and outings are more expensive here than in the Caribbean and Bahamas, as you're in the US and folks are making a higher minimum wage, tourism is a big industry, and everything is more expensive to begin with. That all being said, we live here and we're doing the repositioning cruise in May and the first Alaska sailing in 2014. Happy cruising!