I imagine you’re speaking about the cost of e.g. setting up a wood shop in your garage, rather than the cost of making something in said wood shop. Training this seems more like the latter, while the comparable cost is the former.
If your hobby is building wood furniture, a wood shop helps you do that hobby into the future. It will improve your projects, and help your enjoyment of your hobby. The tools also hold some sort of residual value.
If your hobby is building AI/ML models, a one-shot trained model isn’t going to really help you on an ongoing basis. It’s an amazing single shot project, but if your hobby is actually ML then you probably aren’t going to be happy just looking at your completed trained model - you are going to want to train a bigger, better model.
And if your hobby is building software, you can just download a pre-trained model for free.
You can download a pretrained, full size GPT-2 for $0. Training it from scratch would be merely for fun. You can fine tune the model if you have a specific application for far, far less cost ($0-$10).
It's not comparable to a hobby. It's comparable to paying $10k to make a sandwich.