Artech's website lists it for $895! That's 36% of the cost of the table itself. So $700 is already a discount. I got mine on ebay for $500.
I haven't A/B'ed with the original power supply, but I thought I did notice a improvement in "stability and authority", and you do get an external speed control adjustment (you have to unscrew the case to get to it inside the stock power supply). But $895 worth or $700? No. I find it hard to justify the $500 I paid for it.
I don't know what Artech is thinking with this kind of pricing structure, or what Michell is thinking letting them set prices like that.