I always look at it like this...

If you don't have a whole lot of gold, then farming your own stuff...
Whether that is herbs, ore, skin or cloth to sell...
Or whether it is mats for a combine...

It all makes you a decent amount of gold for your time, and is basically pure profit.

Once you have a bit of capital to work with.
And you want to mass produce something.
You're likely better off buying the mats and making it... for a smaller profit per piece.
But doing 35 transactions at a profit of 50g each...
Then you are in farming everything yourself, and making one transaction in the same amount of time that makes your 300g.