The SpursEngine certainly is easy to come by, in the form of the card from LeadTek. Its reasonably priced (about $160 retail) and readily available in stores. However, it seems they are just pushing it as a short term video transcoding accelerator, with no planned roadmap.
It took them a while to get a Windows SDK out. It took them over a year to make Linux drivers available. The Linux drivers are binary only for a couple of specific RHEL Linux kernels, which are not up to date ones. LeadTek told me they have no intention to make 64 bit Linux drivers available at all. This doesn't sound like a product line with a bright future.
Your comparison is only reasonable for a very small number of tasks. A lot of tasks can extract a large percentage of the available FLOPS from a SpursEngine. Only a very few tasks have been able to use more than a tiny percentage of the available FLOPS on GPUs. Fermi is supposed to change that somewhat, but we will still have to wait and see. Right now many applications run substantially faster when they are not offloaded to the GPU.
The LeadTek card is half the price you quoted. Are you being ripped off? :-\