Paradigm does, the DSP series and they are considerably cheaper. The 3200 can be bought for nearly half the price of the 500 or the 3400 for $300-400 less than the 500. I think that is the only real competition. I have not seen any other manufacturers using DSP, but do they need to? The EP350 works incredibly well, doesn't use DSP and is priced right in comparison to the competitors.
Maybe Axiom needs to bring out non-DSP versions of the 600/800 for those that want to experience the upper end of Axiom subs without the higher costs associated with their DSP technology.
The EP500 goes lower than the Paradigm's. The EP500 also has more power. Those differences may not be worth the delta in price to everyone, but I mention it because you need to compare apples to apples when talking about price.
For Canadians, the EP600 and EP800 are not that far off in price when compared to SVS:
EP600 landed cost $1957
SVS PC Ultra 13 landed cost $2089
EP800 landed cost $2542
The EP600 and PC13 are comparable, the EP800 is an upgrade over either one.