What's amazing is how many companies who buy expensive firewalls for their corporate networks to do this on purpose under the illusion that somehow having LAN computers not being able to access anything besides outbound HTTP and HTTPS on the internet makes you more secure.
Haven't they noticed that everything piggybacks on top of HTTP/HTTPS these days? Even VPNs. You're protecting nothing.
Blocking outbound traffic at layer 3/4 does not require an expensive firewall. It provides protection against certain attack vectors, but as you say, most stuff nowadays uses http/https and in the case of trojans, likely reverse shells. Any firewall should be able to do this.
The expense usually comes in when doing application layer filtering and/or transparent/active proxying, which is the point at which you can block SSL VPN clients and the like. To do this over HTTPS it obviously requires MITMing TLS traffic, which I have mixed feelings about.