First you do a LOT of sewing. Many of us (myself included) only do quilting. I don't do garment sewing anymore. Haven't made a costume in decades.
You sound like someone who gets a great deal of pleasure from all your sewing so that in itself is enough justification.
Plus you have never treated yourself and you have the cash. So I say go for it. It will most likely be the last sewing machine you ever have to buy.
As far as you delimma between the two models and the $600 difference. You have to ask yourself is the laser light and electronic pen really worth that much? and will you really use it? You are right that $600 will buy a whole lot of fabric. Only you can decide if those two extra gadgets are worth the extra expense. I think I would go for the fabric, but that is just me.