TL;DR: GGG for some indescribable reason made the zone level the LEAST IMPACTFUL modifier on relic value.
I've been super frustrated with the garbage marker value of relics from normal heists, even from red map level zones. Sometimes they'd be expensive, most often they'd be as low as white map level relics. This is a problem, because Grand Heist costs are practically exponential as you climb zone levels, while marker income isn't. So I spent an hour trying to figure out what causes the variance in relic value from normal heists.
It's apparently really simple. Each relic has its own base value, based on its rarity (which arguably makes sense from an immersion perspective, but is garbage for actual playability). The most common relics (like Urn of Farud) have a base value in map tier contracts of around 550 markers, while super rare relics (like Ancient Seal) have a base value of 1100. So, y'know, cool. Huge variance based on a total non-skill factor.
You'd think rarer relics would be more common in higher level maps, yeah? They aren't. Ratio from hundreds of banked contacts says otherwise. I had exactly one Ancient Seal contract and it was from a Lv78 zone. Urn of Farud is still stupid common at all levels (as is other garbage tier relics like the Admiral Pipe).
So the second modifier on relic value is the Rogue Job Level requirement of the contract. Playing around with a bunch of contracts, there's no real consistent modifier, it just seemed like every job level above the first adds a 10% or so modifier to the relic value. Level 3 requirement adds 20% value, Level 5 would be 40%.
Now map tier does have a slight impact on this, as white maps can't roll anything above a Job Level 3 requirement, while red maps can roll Job Level 5 requirements. But there's extreme weighting on this; in red maps you're going to be burdened with mostly Level 3 requirements, a decent amount of Level 2/4's, and Level 5 is extremely rare.
Finally, the zone level of the contract does impact marker value! Each zone level above Lv68 adds a staggering...5-10 markers per level. That isn't a joke; identical contracts of Lv80+ zone areas compared to a Lv68 zone, with the same relic and job requirement, are barely a handful of markers more valuable.
This means that an Ancient Seal Lv68 contract requiring Job Level 2 will reward you with more markers than Ancient Seal Lv83 contract requiring Job Level 1, despite the latter having obscenely difficult mobs that are practically on par with endgame bosses by their damage output.
So GGG designed relic value to have a bunch of arbitrary, almost entirely out of your control factors that are so poorly implemented that the hardest possible contracts are entirely capable of being worth less than a T1 map contract. Further, the variance is not just bad, it grows on a linear scale while Grand Heist costs are exponential, so you have to run far more lethal Lv83 heists to run a Lv83 Grand Heist than you would Lv68's of each. And to top it off, marker drops in maps never increase--you're getting 30-50 markers per drop regardless if it's T1 or T16.
It is not a wonder, all things combined, why Grand Heists feel prohibitively expensive, especially at higher tiers--marker income scales at a sluggish, linear pace compared to costs.
