You are right that you would see more on a one way. Some people recommend a round trip if you aren't going to do a land tour also, but we did the one way only and loved it. If you can swing the land tour, then a one way with land tour is my recommendation.
Alaska is expensive. Cruises only go from May to September, so there is a limited number of cruises to choose from. Also, in Alaska, everything has to be flown in, so prices are high. All this effects the price of your cruise and tour.
Alaska is so beautiful that you could go again and again and again without getting tired of it. Be sure to get a balcony so you can view the spectacular scenery from the comfort of your cabin. It is worth waiting another year to be able to get a balcony and tours if that is what it takes to get the most out of Alaska.