▲此题答案确实应选B。句中的 even more so 相当于 they are even more expensive。即：

Programs are expensive, and even more so if you have to keep altering them.

= Programs are expensive, and they are even more expensive if you have to keep altering them. 购买计算机程序（如软件等）很贵，要是还得不断地更换，那就更贵了。

▲下面这个句子是2012年高考英语安徽卷的一道试题，其中也有even more so：

Interest is as vital to learning as the ability to understand, even more so. 对于学习来说，兴趣与理解的能力都至关重要，兴趣甚至更重要。