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

Thematic Equivalence

The current third level ability Warrior of the Gods states that your soul is marked for endless battle. The functional aspect of this is that when you die and someone casts a Resurrection type spell there is no material cost for the casting. This allows the zealot to more easily return to keep fighting for their God(s).

In a world without resurrection, what can give this flavor without making the Zealot overpowered?

My idea riffs off Yakk's, but introduces some additional consequences. While I really liked the idea presented, I think that it is much more powerful than the original.

The original still requires a caster and for them to expend at least a 3rd level spell slot - if not higher. Additionally, unless Revivify (PHB, 272) is cast, there will be a fairly steep mechanical penalty for the resurrection. Namely:

The target takes a -4 penalty to all attack rolls, saving throws, and ability checks. Every time the target finishes a long rest, the penalty is reduced by 1 until it disappears.

In order to balance the Zealot's 3rd level ability in a world without resurrection, similar penalties need to be incurred. The following is my suggestion:

Warrior of the Gods

At 3rd level, your soul is marked for endless battle. When you take damage that reduced you to 0 HP or suffer and effect that would cause you to die while raging, you may instead use a Rage to return to life with 1 HP and gain temporary HP equal to 1/2 your maximum HP value that lasts for 1 minute. You will also be exhaustion level (4). Once you do this, you may not use this again until you have completed a long rest.

Exhaustion Level 4 (PHB, 291) has the following effects:

1. Disadvantage on ability checks
2. Speed Halved
3. Disadvantage on attack rolls and saving throws
4. Hit point maximum Halved

The balance explained

In the original ability, it was required to find or have a caster who had the necessary spell slot available. When coming back (except for Revivify), the penalties are also very big. Allowing the Barbarian to bring themselves back is a big boost, as it becomes an on-demand ability. In order to mitigate this, I have set up a once per long rest mechanic. This way, the Zealot is immediately back up, but with many of the penalties typically given to a creature who has been resurrected.