[TIP] How to fuse +stat eggs in Puzzles and Dragons efficiently

Fusing costs 100g x level of the base monster.
Fusing a monster with +stats costs an additional 1000 x the *sum* of the plus modifier of the base and the "fodder" monster.

If you are fusing a fodder monster to a level 7 base monster, it costs 700 gold (100 x 7).
If you are fusing a +1 fodder monster to a level 7 +5 base monster, it costs 8700 (100 x 7 + [7+1] x 1000) gold.

As a result, it's way cheaper to combine multiple lower stat monsters together before doing the final fusion.

Let's ignore the level for the moment.  Let's presume you are fusing 5 +1 monsters to a single +10 base monster.

If you fuse them directly (even if it's at the same time), it will cost:
([10+1] x 1000) * 5 = 55,000 gold.
(base monster stat bonus + fodder monster stat bonus) x 1000 * (number of monsters)


If you fuse the five fodder monsters together first, then fuse the resulting monster to the base monster, it costs:
([1+1] x 1000) * 4 = 8,000 gold for fusing the five fodder together into the "intermediate" monster
([10+5] x 1000) = 15,000 gold for the final fusion
...which sums to 23,000 gold.