This is pretty much exactly what I wanted (yay for custom images) but the pricing makes it a non starter. Please consider a tiered monthly pricing based on build minutes.
I don't understand what makes the pricing a non starter. You mean the license pricing? If so, 300€/year for something that will save you thousands doesn't seem too expensive to me. If you're talking about the instances, it is 10x cheaper than comparable GitHub runners (i.e. same as ubicloud), so not sure what's wrong here :)