Why can I not change a cost?

Only an owner or an admin can change costs. If your role is Analyst, the cost pages open for reading only. You can open every cost and read it, but its fields are greyed out.

Where the save button would be, the panel says Only an owner or admin can change costs. The same goes for the Default lead time on the Products page: you see the number, but you cannot type in it. Lead times, weights and packaging sizes follow the same rule.

To change costs, ask the owner of your workspace for the Admin role. The owner manages the team in Settings, then Team. An Admin can change costs, but not billing and not the team.