For what reason are the glucose strips for the Contour next double the price of Contour Blue Plus model?

All glucose meters are manufactured to the same accuracy standards so I wouldn't let the accuracy be a factor in making your choice.
Who knows why one type of strip is more expensive, it's probably got more to do with what they think people will pay
Maybe the contour next has more bells and whistles than the blue plus model, so the manufacturer thinks they can get away with charging more?
Thing is, in my opinion, once you have a meter it's the strips that are the ongoing cost and when first testing you get through lots of strips. To me the price of the strips would be more important than any bells and whistles or claims of superior accuracy.

I have a Contour Next connected meter. It seems to work the same as the Contour Plus Blue. They both work with the Contour Diabetes App. See https://www.diabetes.ascensia.co.uk/products/contour-plus-blue/

I saw both products when I was looking for a new meter. I think the Next is the more recent product. The Plus Blue looks to be very good.

My old glucose meter was an Accu Chek Mobile, which has now been discontinued. It has a cassette of 50 test strips which you have to use within 90 days. I hadn‘t tested for a while, so I bought a new test cassette and did a few tests. I was shocked that I was getting some high readings in the 8-10 range and I began to doubt the accuracy of the meter. So I did a search on “most accurate blood glucose monitor” and the meter that came up most in searches was the Contour Next … https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5505415/ - see table 2. See also https://www.medicinenet.com/which_glucose_meter_is_the_best/article.htm

So I bought a contour next. It is probably a bit more accurate than the contour plus, but the plus blue looks to be very good as well. The don’t sell the contour plus in some markets but they still do in the U.K., presumably to compete against other low cost meters.