It goes up of course. Nothing's for free. Don't expect DigitalOcean level of pricing, the premise of cloud is on efficiency and scale, not necessarily being the cheapest raw computing provider when compared to traditional hosting. In other words it increases the elasticity of computation, but the price per unit of computation goes up. (Of course there are cost-savings like ops, security, uptime etc. But if you are talking about one-off side projects or something ML-related then the raw compute/bandwidth costs far outweighs everything else.) For PaaS the free tier is subsidized by your enterprise and other paying customers.
Not sure why you write "of course" and "nothing's for free". If you use dedicated hosting with something like Hetzner, "suddenly hit a big traffic" doesn't automatically mean more costs for you. The website might get slower, or even crash, but your pricing will still be the same as it was before.
https://scaleway.com prices their base compute very cheap [0]. They have got DCs in AMS and CDG, but unfortunately, I've not got to use them since their DCs are a bit far from customers.
[0] €2.99 for 2vCPU, 2GB RAM, 200Mbits/s bandwidth.
