As you get into the smaller thin and light notebooks they tend to get more expensive for the same level of performance. It's takes more specialized engineering to cram stuff into the smaller space and more experienced & skilled techs to assemble.
Business class notebooks like the Portege also tend to cost more than the consumer notebook like the Acer Aspire AS5552G.
The dual core i5-2410M has more CPU power than the quad core N970.
Passmark CPU benchmark scores: http://www.cpubenchmark.net/cpu_list.php
AMD Phenom II N970 Quad-Core = 2815
Intel Core i5-2410M @ 2.30GHz = 3309
The TOSHIBA Portege R835 is an excellent option for reasonably powerful notebook in a very portable package.
If you compare the N970 & i5-2410M - check the boxes and use the Restrict button - you'll see that the N970 almost catches up (but does not pass the 2410M) on the Cinebench R10 32Bit Multi-core benchmark.