Dan,
$400 for a 221 Fireball XP is probably market price but my last 2 XP's were purchased for less. Although I didn't buy this actual XP a friend of mine did about 4 weeks ago. It was a stock 7mmBR, Weaver mount, with a red dot sight (Tasco or Aimpoint--Can't remember). Price paid was $425. Add the value of the dot sight and mount and you made a good purchase on a XP (for my purposes) that you do not have to open the bolt face to rebarrel or if you so choose you can use the Zytel stock if you did rebarrel (as long as you keep the same taper). So for my purposes I would rather pay $400 for a BR than I would a Fireball. It all depends on what you want. Since they have not been made for some time now, I wouldn't be surprised to see the price slowly go up.
Ernie