Getting to "100%" on the first shot is not likely to happen. There is variation in result from anxiety, stress, a shot that does not hit the proper spot, I could go on ...
My first shot was .10 ml, and was ok, and I moved up by increments to .13ml, where I was on the way to the ER at 4 hours. The same amount (~.11) can give me a totally satisfactory result, or something less, depending on the day.
I tried all the pills first, not really wanting to do that injection unless I really had to. I'd rather have blue vision than give myself the shot, but the pills didn't work.
My Trimix cost varies. Two vials (2x5ml) cost from $159-$179 (retail, depends on the cost of ingredients that week) including 20 syringes and prep pads. I pay less because of the insurance "agreed price".