Also the Viable part of MVP is subjective. As you build the MVP, your idea of what is viable changes. This needs to be accounted for. The minimum product has to be viable for a paying customer. If the MVP is not a paid product the you can get away with less polish, not so with paid products.
The viable I had in mind was 'it works' - later realised that actually viable was 'I think there is a chance I can ask people to pay for this' - turned out that second part around doubled the already overrun build time!
