You can, and if you want to use Lambdas, you can also route to them from ALBs, which has a bit confusing of a pricing model for comparison, but has no per-request cost.
Oh, ALBs. Now that's a mess. You'll either be charged per new connection, per concurrent connection, per byte, or per rule evaluation, depending on which is highest any given hour.
https://aws.amazon.com/elasticloadbalancing/pricing/