has introduced Photomatix Pro v4. Upgrade pricing is described here
or you can buy a new copy for $99. But if you're a new user then take advantage of their free try before you buy service.
Fortunately my original copy of Photomatix was purchased a few months after the 22 March 2007 cutoff for free upgrades. v4 installed just fine and picked up the v3 (originally v2.5) licence. After installation both versions were left on the computer so I uninstalled v3 manually.