Elastic = Flexible cost behavior → Your bill adapts to usage.

Scalable = Flexible resource behavior → Your resources grow/shrink, and cost follows.

Elastic = Your mobile data plan – only pay for the data you consume.
Scalable = Your Netflix plan tier – scale to higher quality (HD, 4K), you pay more. Reduce it, pay less.

Both are OpEx models that avoid fixed costs.

Elastic is cost-first. Scalable is resource-first.