Rarely, and it carries risk. Trade garment prices are usually below retail, and if we damage a garment we supplied we replace it. If you supply it, that risk is yours.
The other risk with supplying your own garments: if the fabric isn't suited to your decoration method, that's now your problem to solve mid-order, not ours to catch at quote stage. We check compatibility automatically on garments we supply — that check disappears the moment you bring your own stock.
The questions are free. So is the quote.