Not true. For hobby projects, using netlify and heroku is often cheaper, agreed. But for serious organization it might be cheaper. Heroku's standard 2x dynos pricing is $50 per month [1]i.e 1GB mem, whereas a droplet in digitalocean is $5 per month for the same resources[2] with 1000GB storage. Lets add loadbalancer to the mix additional $10 per month, domain and SSL certs are negligible prices, max would be $20 per month. It comes at the price of engineering time.

[1] https://www.heroku.com/pricing

[2] https://www.digitalocean.com/pricing