The base XLStat Pro module was priced around $800 - $900, and this would invariably go up, very possibly into the $1200-1500 range with the addition of other modules. Minitab can be purchased for around $1500 - 2000, so I see XLStat as not a good use of your money.
I purchased StatPlus 2007 software and found it to be very poor quality. It will not accept named ranges, and often fails with a plea to contact the software author to report problems. In my opinion it is not commercial-quality software at present.