Scopes with logic analyzer inputs often have optional add-on modules that let them decode various serial protocols: SPI, RS-232, I²C, CAN, etc. Tek and Agilent want around
US $700 *per protocol family* for theirs.

My question is, why would I want to buy a software module more expensive than Photoshop to do this when there are [many](http://www.bitscope.com/software/logic/) [PC-based](http://www.sparkfun.com/products/8938) [protocol](http://www.pctestinstruments.com/) [analyzers](http://tools.asix.net/dbg_sigma.htm) [on the market](http://www.totalphase.com/products/beagle_ism/) [at a fraction of that cost](http://usbee.com/busbee.aspx), many of which decode multiple protocol families? Are Tek, Agilent, *et al* just soaking EEs, or do these modules have features you don't get with a US $150-400 PC-based protocol analyzer?