The answer to your last question is basically, NO! There are way too many bubbles in alumilite cast without pressure (clear alumilite). The pressure does 2 things. It reduces the size of existing bubbles, but more importantly, it prevents bubbles from forming.
That being said, I too wanted to do my own blanks. Not to save money, but it looked like fun. And for the most part it is. But I think your math is a little off. In a perfect world, you should be able to make an alumilite blank for $2. But here's the real world answer, and lets forget about the pressure pot right now. You'll need a mold. There are flat molds and round molds. If your really serious, you'll want 1 of each (at least). Then there are cups, popsicle sticks, mica powders, and dyes. when I pour, I use wax paper under the molds to contain any over pouring. I'm guessing I go through a roll for every 200 blanks. You'll need latex or nitrite gloves unless you want your hands to look like you have really ugly tattoos. Do you have a place to pour? I made a table just for pouring, but you could buy one of those folding tables from Walmart. A scale isn't required, but it helps, and saves time. So forgetting the pressure pot, you're probably looking at close to $200 in initial start-up. Add $100 for basic colors for mixing. Then the cost of the alumilite. Your 1st 100 blanks can easily cost $400 without a pressure post.
I think you're about right at $2 cost per blank for consumables. But how many good blanks will you get? It won't be 100%, I can promise you that. Out of your 1st 2 gallons, I'll be surprised if you get 75 good blanks that actually become pens. Your ratio will get better, but if you think you'll get 150 pen blanks that you'll use or sell from 2 gallons of resin, you're wrong. There is a lot of waste in pouring blanks. For every color you mix, it involves either 2 or 3 cups depending on your pouring method. Each cup will have waste. And usually, in a 6 blank pour, I'll bet I have at least an ounce of wasted resin. But I have a lot of pours that are only 2 or 3 blanks. And the waste is almost the same. How many blanks of the same kind are you going to make at the same time?
I'm not trying to discourage you. But pouring your own blanks is similar to making pens. Like a lathe being the tip of the iceberg as far as cost, so is the cost of the alumilite to make a pen blank.
