I think you have misread.
This doesnt increase the capacity of an existing DIMM. It allows more DRAM chips to be fitted onto a single DIMM.
This means that, for the same capacity DIMM, you can buy more, lower capacity, cheaper DRAM chips. Alternatively you could buy the higher capacity chips and fit more of them on the DIMM, giving a higher capacity DIMM that would otherwise be possible.
With the products listed in the article, you can see an 8GB DIMM for £100!
I actualy looked into a design for something similar myself, but it was horribly complicated and not worth it for me (I would have been using an FPGA, performance would've been shonky!)
So, there are 2 important questions: 1) is there any way to shoehorn 4 of the 8GB modules into my server (an AM2 athlon64), and 2) can I scrape the £400 together to do it?