The Real Cost Calculation
Most cosplay budgets underestimate costs in three areas: tools (if you don't own a heat gun, craft knife set, rotary cutter, contact cement, spray paint — these add up); shipping on small orders of specialty materials; and the cost of mistakes. Budget 15–20% over your materials estimate for errors, waste, and the inevitable "I need one more thing."
Where to Spend
Spend on: fashion fabric that will be visible and photographed (visible quality difference); the specific detail elements that make the character recognisable (getting these wrong is immediately noticeable); anything structural that determines how the costume wears. Save on: backing fabrics and interlinings (quality matters but premium prices don't); basic hardware; any element that will be painted over or covered.
Tracking During the Build
Keep a running total in a note on your phone. Record every purchase as you make it. Check against your budget at the midpoint of the build — if you're already at 60% of budget with 40% of materials to go, you need to identify where to economise in the remaining build.