NPC happiness planner

Put your town NPCs into groups of houses, pick where you stand, and see each price and mood line the way the game works them out.

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How the game works out the price

Start at 1.00.
With the Lovestruck debuff: x0.90.
In a Remix Seed world, and for town pets: stop here. Nothing else counts.
No home, more than 120 tiles from home, or you stand in the Corruption, the Crimson or the Dungeon: the price goes to the cap, 1.50.
Neighbours: other town NPCs whose homes are less than 25 tiles away. NPCs at least 25 but less than 120 tiles away count only for the space bonus. Town pets never count.
Crowding: x1.05 for each neighbour above 3.
Space: 2 or fewer neighbours and fewer than 4 NPCs farther out: x0.95.
Biome: only the zone you stand in counts. If you are in two zones the NPC has a feeling about, the better feeling wins.
Neighbours the NPC loves x0.88, likes x0.94, dislikes x1.06, hates x1.12.
Every NPC likes a Princess neighbour. The Princess loves up to 3 random neighbours, gets no crowding and no space bonus, and hits the cap with fewer than 2 NPCs near and fewer than 2 farther out.
The result is kept between 0.75 and 1.50 and rounded to 2 decimals.

Happiness does not matter for pylons.
A shop sells pylons when at least 2 town NPCs have a home inside a 169 x 124 tile box around you, and each stands less than 100 tiles from its home. Town pets count here.
No pylons while you stand in the Corruption or the Crimson, and none from these shops: Traveling Merchant, Skeleton Merchant, Tavernkeep.
Which pylon depends on the zone you stand in. The planner lists them for each group.
You can place only one pylon of each type in a world.
To teleport, the pylon you stand at and the one you go to each need 2 NPCs by the same rule, and each must be in its own biome.

Shop prices: you pay the price x the factor, and you sell for the price / the factor.
Nurse: heal cost x the factor.
Goblin Tinkerer: reforge cost x the factor.
Stylist: hair cost x the factor.
Tax Collector: the tax money you collect / the factor.
Angler: quest rewards get rarer with a lower factor (x the average of the factor and 1).
Leading Landlord: talk to a housed NPC at 0.82 or lower.

Read from the game code of build 24893155. The planner assumes every NPC in a group lives less than 25 tiles from the others and is at home.