Are there easier way to do this?
I use MS SQL Server
So it would be, ie. 61
                    62
                    63
                    ..
                    ..
                    610
                    ...
                    6100
                    6200
                    ....

Do the product ids have meaning outside the database? If so it is
probably better to use another field as the primary identifier that
does not have meaning outside the database and so can be an integer.

However, whether you do that or not I think that the best way to
generate the next number is to use a transaction in the insert stored
procedure and first SELECT @NewId = MAX(PID) + 1 FROM Product; and then insert @NewId into the PID for the new row.

I hope this helps.

I think your making things complicated for no reason. Why not use a normal key that is an int and have another field with a unique index with your 6.1 type stuff? You can populate the 6.1 vield with a view automatically if you want. Another thing to ask yourself is do you want to have to go to 6.99 before getting to 7.00?