With Double Crystals Giftbox.

Using Site Shops When Possible
Quests Completed: 100
Cost: 498,314 MP
Time: 50 Minutes (2 Quests/Min)
Return: 1,101,967 MP
Profit: 603,653 MP

Always Using User Shops
Quests Completed: 100
Cost: 725,307 MP
Time: 17 Minutes (5.8 Quests/Min)
Return: 1,023,343 MP
Profit: 298,036 MP


The profit for 100 Site Shops Quests is 603,653 MP and took 50 minutes to do.

The profit from 300 User Shop Quests would be around 894k and would take the same amount of time.

Conclusion: Pay the higher amount for user shops, it is a lower amount of profit per quest, but faster to complete and more profit overall in the same amount of time.