To do this writ you need to craft 8 Psijics' Ambrosia. With max leveled Provisioning it requires 2 Perfect Roes to do that (you make 4 drinks at once).
The avarage price for 1 Perfect Roe is 10000-12000 gold (TTC and MM addons data on PC EU).
The average price for 1 voucher is like 500-1000 gold. It depends on what materials you need to do the writ and how much vouchers you can get as a reward. The most part of Master Crafter writs on the market gives you 1 voucher for every 500-1000 gold you spend on a writ and crafting materials needed.

Now, let's see. You buy 2 Perfect Roes to craft 2 Psijics' Ambrosia (20000-24000 gold) and you get 10 vouchers. So, you actually could throw this writ away and go buy any other writ and get the same 10 vouchers for like 5000-10000 gold spent on crafting materials.
Moreover, even if you have your own 2 Perfect Roes (so you have not to buy it for 20-24K gold) you can craft 8 Psijics' Ambrosia and sell them in a guild store. It will give you 25000-30000 gold (3200-3700 is average price for 1 Psijics' Ambrosia in guild stores). Then you can buy and complete any 25-30K gold worth Master Crafter writ. So, you can actually get like 50-60 vouchers "for free" if you have 2 Perfect Roes.

That's it.
What's the point to do Psijics' Ambrosia writ for 10 vouchers?