Perhaps things have changed somewhat since then though
I think what has changed is that piston twins cost even more than they used to
They guzzle fuel like it was going out of fashion, they cost a lot more to maintain (not least because most of them are old, and it looks to me like a lot of their owners run them down
because they have a spare engine), and keeping the pilot paperwork current costs more.
But if you want the extra motor, for flying at night / over terrain / over water / etc because it makes you feel safer, then there is no contest.
And at the top end, say a 421, you do get an awful lot of load carrying capability together with a lot of weather capability (~FL250 ceiling, pressurised, deiced, radar) which has never been delivered in a single, presumably partly because nobody produced a piston engine big enough. It is only the 700+ HP turboprops (TBM, PC12) which deliver that sort of capability (and more) in a SE, but at a far higher purchase cost.