The combination of raise dead and restoration in Pathfinder RPG is not only reasonable, it's intended.
The price difference is a holdover from D&D 3.5, where the combination of raise dead and restoration was actually much weaker than true resurrection. In D&D, raise dead caused a full level loss instead of a negative level, and restoration could not restore the lost level. As the only spell able to revive a character without level loss, true resurrection was significantly more valuable.
In Pathfinder, restoration was explicitly given the new ability to recover permanent negative levels, at the increased price at 1,000gp per level. This suggests that the designers intended for the combination to be available.
Even so, true resurrection still has advantages:
- You don't need an intact body, which is useful if the body has been maimed, disintegrated, captured, dropped down a pit, or left behind after fleeing
- You can raise someone who's been dead for 10 years per caster level, instead of 1 day per caster level, which is useful if you took too long to drag the body back from the wilderness
- The character returns with full hit points and prepared spells, handy if you absolutely have to fight something right away
- It only takes 10 minutes to cast true resurrection, whereas restoration can only heal one negative level each week
- You can raise someone even if they were killed by a death effect, or killed and turned into an undead
- You can raise elementals and outsiders, if necessary