whatever you prototype - the one who built it in 6 month will have economy of scale to make it cheaper than your diy solution, and because they serve many customers and developed it for 6 months - their product will be 100x better than the one you diy

there is very very rare use case when diy makes sense. in 99% of cases its just a toy that feels nice as you kinda did it. but if you factor in the time etc it is always costs 100x more than $5/month you could usually buy

With that logic LEGO sets and Salesforce subscriptions should be virtually free due to their economy of scale

Based on your earlier comment and your last paragraph, your impression of AI vibe coding ability is at least a year out of date.

In late 2024 it might have taken 6 months. Today, two weeks, maybe 3.