I find it can be relatively quick to write a prototype that does 90% of what you need with a few critical bugs but to get it finished, mostly bug free and with

I find it can be relatively quick to write a prototype that does 90% of what you need with a few critical bugs but to get it finished, mostly bug free and with high quality concise code can take a lot of time. It can take a while to understand the problem fully and understand the common patterns in the code that lets you find the right abstraction that will simplify it all.