There is always solution for a particular case. But what about cases without any commas?

Here is one proposal:

declare @amt varchar(20)

set @amt = '10,000,000.00'

--desired is 10-000000.00

set @amt = substring(replace(@amt,',','-'),1,charindex('-',replace(@amt,',','-'),1))+substring(replace(@amt,',',''),charindex('-',replace(@amt,',','-'),1),len(replace(@amt,',',''))-(charindex(replace(@amt,',','-'),'-',1)))

print @amt

IgorMi