Finnish society has already shown this willingness to pay. All mainstream political parties support the existing welfare state for the most part, and any Finn knows a few people who live on benefits and want to avoid any kind of hard work.
Furthermore, over the 20th century the Church and other forms of private philanthropy have dwindled away in Finnish society. The average Finn today does not want to have to make an effort to personally help out other people, and engage in uncomfortable social interaction, even if we are talking about their neighbours. (After all, those living in blocks of flats rarely even know their neighbours.) So, Finns are quite happy to have a wide social safety net provided by the state – even if it is sometimes "abused" – in order to save them the effort of returning to a charity model where real effort and personal interaction would be expected of them.
As it pertains to other people, I see it as a floor that will hopefully help people unlock their potential by taking some of the pressure off the exchange of time for wages and focusing it on the meaning of work.
If people want to do nothing beyond their UBI income, that's fine - but I don't see this being a widespread phenomenon. It covers the basics, and we have a tendency to yearn for more.
1. They are usually time limited. You can expect different behavior if you get financial security for limited time or for life.
2. Most studies seem to be externally financed (here the whole state vs a small population). The interesting part is if people are willing to pay for this within their community. Are you okay to pay for your slacking neighbor (even if she is the exception and UBI turns out to be overall good)?