Fused suits is where they literally cut out your size and glue the front and back of the jacket together (therefore breaks on contact with water). Half Canvassed has a half "filler" in between the suit so that the front and back does not stick together so that it falls naturally but obviously the bottom half can stick. Full canvassed has a full filler for natural drape. End bolt simply means left over wool from a bolt of wool where some other guy used to make his suit. Left over bolts might only have enough for one other suit so the price is usually discounted in order to get rid of that bolt.
The part on the inside which touches the skin (if that is what you are refering to) is the suit lining. Top of the line silk or a Bemberg liner will usually get you what you want. However, you said this is a summer suit so I'd suggest a half lining so that it breathes better (fully lined suit will trap heat). Otherwise if you are asking about when you or other people touch the outside of the jacket and its smooth, then you need to get a wool swatch book and see which pattern and wool you think feels good. There are a lot of summer wool but some are expensive. Scabal, Holland & Sherry, and Loro Piana for instance are the premium quality wools that I was talking about before. If you touch their swatch compare to other wool, you can tell the difference in an instance.
So in some ways, yes the quality of the wool, and the lining of the suit is what dictates the pricing. But you also don't want a guy that uses more wool because he screwed up the shoulders and ends up charging you for more wool. I am also very picky and request certain areas to be hand sewn which will drive up the price as well.