求助：prep 1-28

First-time computer buyers buying PXC home computers typically buy models that cost much less and have a smaller profit margin per computer than do PXC computers bought by people replacing their computers with more powerful models. Last year PXC's profits from computer sales were substantially higher than the previous year, although about the same number of PXC computers were sold and the prices and profit margins for each computer model that PXC sells remained unchanged.

If the statements above are true, which of the following is most strongly supported by them?

(A) PXC's competitors raised the prices on their computers last year, making PXC computers more attractive to first-time computer buyers.

(B) The number of people buying PXC computers who also bought PXC computer-related products, such as printers, was larger last year than the previous year.

(C) Among computer buyers who bought a PXC computer to replace their existing computer, the proportion who were replacing a computer made by a competitor of PXC was greater last year than the previous year.

(D) The proportion of PXC computers bought by first-time computer buyers was smaller last year than the previous year.

(E) PXC's production costs for its computers were lower last year than they had been the previous year.

D是正确的，可是为什么E不对呢？既然生产电脑的成本降低价格也基本持平那利润应该就会高，也可以支持题目的argument咯？

请NN帮忙解答，谢谢