Working on a custom race, I decided to go back to the PC and figure the XP cost for custom racial powers, using the level-0 costs and powers for each of Dwarf, Elf, Gnome, Nobiran, Thrassian, and Zaharan. Here's how the XP came out:
Dwarf: 5 powers, 200 XP, 40 XP per power
Elf: 4 powers, 125 XP, 31.25 XP per power
Gnome: 7 powers, 250 XP, 35.7 XP per power
Nobiran: 4 powers, 125 XP, 31.25 XP per power
Thrassian: 6 powers, 200 XP, 33.3 XP per power
Zaharan: 3 powers, 200 XP, 66.7 XP per power
Note that the Zaharan has 4 positive powers, but the Dark Soul is a negative power, which brings it down to 3. Going by other racial costs, the Zaharan seems like it should be around 100 XP (and Dwarf should possibly be 175 instead of 200, which would drop it to 35 XP per power).