"DSI cards" is ambiguous. Please specify which you mean:
Possibilities
Nintendo DSi Points Cards (Prepaid): Discontinued 2016. Were sold in denominations: 1000 pts ($10), 2000 pts ($20), 3000 pts ($30). No longer sold officially; secondhand codes on eBay ~$15–$40 (collector markup).
Nintendo 3DS / Switch eShop Cards: Current. $10, $20, $35, $50, $70 at retailers (Target, Best Buy, GameStop, Amazon). Digital codes via email instantly.
DSi/3DS Flashcards (R4, Acekard, SuperCard, etc.):Piracy devices. Illegal in many jurisdictions (DMCA, EUCD). Sold on grey-market sites ($15–$40). High risk of bricking console, malware, legal action. Not recommended.
DSI (Data Systems International) Gift/Membership Cards: Unrelated to Nintendo. Contact the issuing organization.
DSI (Dynamic Systems Inc.) Security/Access Cards: Industrial. Pricing via vendor quote.
Reply with the exact context (gaming, corporate, security) for a precise answer.
