I've been burned too many times on too many different things. I'm done with agreements, everything moving forward, strangers to family (especially family) will be done with a signed contract.

Last deal sucked so bad it inspired a pair of tattoos to remind me.

As for materials pricing, my father taught me a long time ago, round up, then estimate 1.5x that cost. if you can 'just' get three pieces out of a stick of wood or length of steel, then figure you need two sticks.

I factor in consumables on what I think I'll need, a bit over or under balances itself out in the end.

Labor I routinely screw myself on, but I charge between what's fair (high side) and what I can get (low side) and figure a bad day in the shop is better than a good day at work