How to determine your markups?

Pricing can feel like a total guessing game sometimes, especially when it comes to markups. Every designer seems to handle it differently, and there’s no “official” rulebook to follow.

Curious — how do you figure out your markups?

Do you stick to one percentage for everything?
Do you change it depending on the product, the vendor, or how much work it takes to source?
Do you build in things like shipping, storage, or project management time?

Not looking for trade secrets- just hoping to hear what’s been working for you and how you keep it fair for both you and the client.

Can’t wait to hear everyone’s approach!