It's true that they do seem to jump dramatically. You can adjust the height yourself though. It's just fiddley, but I did it with the three sets that I bought =- you pull out the extra slats and re-tie the cords. It just takes some time. I know what you mean about having to pay more when you want less. I guess they're matching to the most commonly-sized windows?

Yes, I had them cut in-store while I waited. Give them the measurement for either inside your window casing, or the full size you want if installing overtop your window.