Call it a hunch, but i think net worth is something like
Cash on hand + (total ship worth) + sum(gun worth) + sum(projectile worth) + sum(parts worth) + sum(repair worth) + sum(commodities)

Basically, everything you have on you. When i tractored in a Hessian gun one time, i leveled up. Consider a market system. When you tractor in loot, you add to your worth. Selling them turns it into cash, so a transfer of funds stays consistent. The more you tractor in, the more you're worth.

Hope that helps.

And the more you buy cheap and sell for a good profit

I'm sure WJDragon is pretty close:

When leveling up, It usually is a pain when you hit those even levels, since that usually means new guns if not a whole new ship = lowered net worth. I'm not completely sure, but I think I left a station (after said even level up purchasing binge) and went back (forgot my purs.. I mean, beer bottle.) and found my net worth lowered -- since ship parts are only full-priced for selling back when you purchased it.

But...it has to be something more than that, too.

Case in point:
I bought a full load (250) of...uh..some commodity for 22,500 credits. I watched my net worth, and afterwards, I was worth 52,500 more. Where'd that other 30k come from?

I think it has something to do with color, too, or maybe mean price. I bought the above at a green price, by the way.

I also tried buying a commodity at a yellow price, and it said I lost money. Not exactly sure why, I may try experimenting with it later.

grav