Well they have since how long? 1980's when the Barnett formula kicked in? Irrelevant though...the fact is we go solo now...it will destroy us.
Actually that's the point. The Barnett formula only gave back to Scotland some of the extra money that was raised in Scotland from oil. Until 2014 Scotland had been sending more per capita in tax to London than it was receiving back in extra spending every single year since at least the early 1970s.
See this table that shows higher tax receipts per capita in Scotland compared to the UK for the last few decades.
http://www.gov.scot/Resource/0041/00418381.pdf
Only very recently has this trend changed. London has not been sending Scotland money, it's been the other way around.
The idea that London will send Scotland extra money indefinitely despite falling tax revenue from Scotland is a leap of faith.
In fact London politicians have stated the opposite: that Scotland in future needs to raise its own taxes to cover spending.
So I ask again what makes you think London is going to send extra money to Scotland for decades to come?