In my experience, "budgeting curveballs" are a symptom of issues that were left unresolved at the early stages of development. Too many designers with skill gaps try to DIY thinking it will save them money, when it can end up costing more or they have to reduce features that may affect the integrity of the design if the budget is limited.

To stay on budget, I'd switch to more affordable fabrics or trims without losing quality, simplify the design to cut costs, and negotiate better deals with suppliers. I'd also adjust other parts of the budget to cover the essentials and keep the project on track.

Pedindo orçamentos e amostras das matérias primas a várias empresas, para poder escolher a melhor opção tendo em conta a relação qualidade/preço. Procurar materiais alternativos, mas com qualidade. ...

Based on my experience, I’ve learnt that it is better to cut quantity than to compromise on quality, especially if your business is built on serving quality, well crafted goods.