Tickets can and do sell out. If you wait until you arrive at the gate, you risk the park being at capacity, making your travel costs a wasted expense.
When purchasing Disneyland tickets, the price for a standard admission is typically the same whether you buy it online or in person at the gate. However, buying online is almost always the "cheaper" option when you factor in time, availability, and potential third-party savings. cheaper to buy disneyland tickets online
Scammers may sell a ticket, report it "lost" to Disney to get a replacement, and leave you with a deactivated barcode. Tickets can and do sell out
Buying online allows you to skip the long ticket booth queues, which can save you an hour or more of prime park time. How to Actually Save Money Online However, buying online is almost always the "cheaper"
Trusted sites like Undercover Tourist or The Park Prodigy often provide slight discounts on multi-day tickets that you cannot get at the physical ticket booth.
Organizations like AAA or warehouse clubs like Costco (in select regions) sometimes offer exclusive online-only ticket packages.