The synthesis support item in question is the Carpenter's Ring. This provides a 1% decrease in failure rate, but removes the possibility of a HQ synth. Your chance of getting a Cursed Togi -1 is only 1-2%, but using the ring will make it 0%.
As far as whether it's economical, I'm pulling Cerberus info off of FFXIAH. On your server, a Cursed Togi is selling for about 1 mil (however, was just about 700k a month ago, so watch for price movement). Divine Logs sell for about 400k. The rest of the materials are not an issue, about 10-15k.
I'd go through all the math here, but it's long-winded. Basically, over the long run, with breaks from lumber and togi synths, the expected value of a Togi would be about 875k. Thus, it would currently make some sense to go this route. However, you're not doing this 100 times. You're doing it once. You have 3 synths to attempt this way, each time risking a 4% chance of loss. On the first two you risk 400k, on the last one you risk the whole thing. That's a 12% chance of something ruining your plans.
Long story short you have two options:
1. Take the risk. If it works you save 180k. There's an 8% risk you'll lose 400k from a log break, and an additional 4% risk you'll fail the Togi and lose it all.
2. Play it safe and pay the 1 mil, or wait for the Cursed Togi prices to drop some more. The prices on those are kind of volatile, and will have spikes and valleys depending on supply/demand.
Personally, it doesn't take me long to make 180k profit in other places. For a one-time synth, I'd rather pay the extra amount and be done with it.
Edited, Mar 9th 2009 3:31pm by Doomfist
[ffxisig]184415[/ffxisig] Red Mage for Life! Bastok Rank 10 Windurst Rank 9