Almost $.40/hour, you need one per AZ, and it’s $.06/GB for network traffic. I’m happy to see the capability (mainly outbound URL filtering), but this looks like it’s going to be a hard sell to my managers. You’re probably looking at a grand per month per account. On the plus side, they don’t double charge for NAT gateway traffic.
For large enough enterprises, $1k a month is a rounding error. Also, depending on how you're provisioning accounts and laying out your networking, you may not want to be sticking one of these in every VPC. There's no one-size-fits-all, but in many cases a transit VPC that handles the egress centrally would make more sense.
Even though $1k is indeed a rounding error where I work vs. what we pay each month, it's becoming annoying how granular the billing for new setups is becoming. When I'm asked to compare TCO of an on-prem solution vs. a hosted one that includes all-of-the-above, I feel like I'm playing actuary and not cloud engineer.