- Does this mean that if I begin crafting a Phylactery at level 11 it will cost me 120,000 gold and take 240 days?
In theory, yes.
The lich template is the only source I found that says the phylactery costs 120,000 gp to create. Since the crafting cost is usually 50% of the market price, I suppose this means that a lich's phylactery has a theoretical base price of 240,000 gp.
According to the rules on magic item creation, crafting a magic item normally takes 8 hours per 1000 gp in the base price, working up to 8 hours per day. This would translate to 1 day per 1000 gp in the base price. This also assumes you aren't adventuring and have sufficient space and concentration for crafting.
So a base price of 240,000 gp would normally require 240 days. This time can be reduced:
This process can be accelerated to 4 hours of work per 1,000 gp in the item's base price (or fraction thereof) by increasing the DC to create the item by +5.
In most cases, this means you can craft at double speed, i.e., complete the phylactery in 120 days.
Additionally, if you (and an ally) both have the Cooperative Crafting feat, then you can double the speed again, i.e., complete the phylactery in 60 days.
- Also, is the caster level of the item the level I am when I begin crafting or when I finish crafting?
It's when you begin. The material cost is determined by your caster level, and the material cost is paid when you begin crafting.
The character must spend the gold at the beginning of the construction process.
Therefore, the item uses the caster level of the crafter when they began making it.