A Head of Demand level 70
Each Turnin of HQ items will grant a reward of 4,164,300 XP and 6,400 Gil. You will make a gil profit if you can obtain the 1 items for less than 6,400 each.
You will only gain the listed XP amount if you're within the Expansion's Level Range; A level 70+ character attempting to complete a level 60-something Leve will gain almost no experience.
Because this is a Repeatable Turnin, using one leve allowances will net you 3 turnins, as opposed to 2 allowances allowing only one turnins with other leves.
Most likely you will stop doing this leve after 5 levels, but depending on market prices/etc it may be benefitial to keep turning it in well past that. Also remember to Diversify. The same quest will not always be available to choose.
Use your best judgement when deciding which level to mass produce.