Mailing a bubble mailer can be cheaper than mailing a box, depending on the weight, size, and destination of the package. Bubble mailers are made of a lightweight material, which can make them less expensive to ship than a box. Additionally, bubble mailers are pre-formed and do not require any additional packing materials, like tape or cushioning, which can also save on shipping costs.
However, if you are shipping a large or heavy item, a mailing box may be more cost-effective because bubble mailers have weight and size limitations. Also, if you are shipping a fragile item, it might be more suitable to use a box with cushioning materials like foam peanuts or bubble wrap.
It's also important to consider the shipping service you choose. Some shipping services offer flat rate pricing options for different types of packages, which can make it cheaper to ship a box than a bubble mailer depending on the weight of your package.