If someone only wants what can be crafted and were to buy all the minions, it would cost about 715K on my server atm (even less if you travel between worlds/data centers). This cost includes all other materials too, including rare materials that can often be sold for more than the minions/mounts on the MB. Each of the minions/mounts listed below requires inter-crossing (save the Allagan Melon) and multiple consecutive days of login for both intercrossing and growing the minions.
Many of these minions can already be obtained from retainers, fetes and GC loot boxes so in reality the total cost is much lower.
Onion Prince 20k
Garlic Jester 39k
Tomato King 35k
Allagan Melon 250 gils (Allagan Melon Seeds take 7 days to grow and cost 300 gil from Merchant. No garden needed at any stage but no reason to grow it)
Eggplant Knight 28k
Mandragora Queen 58k
ROYAL FERN (0 reason to craft any of these minions: just sell the mats from the trials or craft something else - example: the trial mat used to craft the peacock is >400k.)
Byakko Cub 5k
Private Moai 1k
Scarlet peakock 2k
Seitei 2.9k
Magnai 10k
Sadu 10k
Shinryu 1.5k
Glazenut
Atrophied Atomos 100k
Iron Dwarf 41k
Magic Broom 20k (also requires Broombush)
Model Magitek Bit 48k
Plush Cushion 50k
Steam Powered Gobwalker G-VII 110k
Blood Pepper (way too much trouble to grow IMHO vs selling price. I’d rather buy the pepper for the more expensive minions and then craft)
Wind-up Bismarck 850
Wind-up Garuda 14k
Wind-up Ifrit 15k
Wind-up Illuminatus 50k
Wind-up Lakshmi 600
Wind-up Leviathan 15k
Wind-up Ramuh 12k
Wind-up Ravana 1.2k
Wind-up Shiva 7k
Wind-up Susano 800
Wind-up Titan 18k
If you add the Flying Chair (115k - I got several from GC boxes) and Magicked Bed (1.8 M due to rare mats from maps), it is about 2.7 Mil total with immediate, guaranteed and effortless results.
You also have to add a 450k building permit to the purchase price of a small house.
I just grow Lavender indoors and outdoors: it’s easy to grow and I can exchange it for mats that sell well.