It depends from formula to formula. For example the Crimson Accidentaly Archer requires quite some alchemy exclusive items, caches ingredients and 1Bil to craft; the items just require time to get the right ingredients out of the caches and craft them, so it's quite cheap overall, just time consuming. Others can require more gold (up to 10Bils) and different items.
Would you open them for me? *3*
I would also need Aquamarine, Gold and Platinum. You just can't have enough of them lol Otherwise you can sell them: the Platinum one costs 25-30 Mils each :U
At the moment the only ones that seems elusive are Amethyst ones, but are expensive in the MP, I usually open a batch of Alchemist Caches to find the ones I need XD
Anyway, if you see something in the alchemy news or in the Bifrost that may catch your eye, just let me know!