I think unless you’re at serious scale, it will typically work out much cheaper if you’re talking raw compute but it’s not really comparing apples and apples either and depends on how you arrange your application architecturally.
Let’s take Cloudflare for example, they don’t ever charge for egress / bandwidth (except a couple of products - Calls and Stream - but those are naturally quite specific use cases that are high bandwidth).
So if you are able to statically render the majority of your pages, that’s literally free on Cloudflare - images, HTML, CSS etc. it’s all free, unlimited bandwidth. You then only pay for your API calls made from those pages, and the rates are incredibly cheap - 10 million requests/month included in the $5/month plan, $0.30 per million after.
Naturally at some point, there will be a crossover where a VPS will be cheaper - but then it’s not really apples and apples. With a single VPS, you have no failover, no scalability, no disaster recovery and you’re ultimately managing that VPS yourself. With Cloudflare, you basically get all of the above included (AWS would call this undifferentiated heavy lifting). You don’t have to worry about scaling, as the Workers will just scale to meet demand, and even if an entire contintent goes down, your requests will be served from another continent - and naturally , no maintenance.
So there’s no definitive answer because it depends entirely on use case and how you structure your application, but there are large companies making use of Cloudflare at enormous scale - so it’s definitely viable to build large businesses on it too.