So I've been finding flowers around the site and I read the announcement about the Vesnali event but I still have a couple of questions.
the coins are created out of thin air by the giving/getting flowers.
There is no official exchange rate between sP and Vesnali Coins. The coins gotten from the flowers can vary in price from 3000 to 40000 subetapoints apiece, depending on demand of the new items, how many new items there are, how many coins are left over from last year, whether or not there's being any immediate retiremenes from Esther's etc.
If you are interested in maxium sP return, you may get more from selling the flowers themselves, because users collect them. Do a buncha Shop Searches each time you're thinking about selling to see what's currently the best deal.