Reading in from Excel via VSTO is about 10-100 times slower than from VBA

I have a .net 3.5 application with an Excel VBA front end.  Some of the data (e.g. 10000 rows with 150 columns, spread across different worksheets) is stored in Excel, and whilst reading this in from Excel VBA takes about 2-3 seconds, it takes minutes to read in the same data from C# using VSTO (Visual Studio Tools for Office).  
Is this an inevitable consequence of the fact that VSTO has to treat each Excel Cell as of type Object, and has an overhead of talking to and from Excel via the Primary Interop Assemblies, whereas VBA is already within Excel?  
I am not reading in each individual Excel cell (which would slow things down even more), but am reading the whole of each Range containing a rectangular block of data into an array (see code snippet below).  
However, because the array has to be a two dimensional array of type Object, I then have to convert each cell into the appropriate type (DateTime, int, double, string etc.) which probably adds to the time.

Am I missing something?  If not, then Microsoft should be aware that the slowness of reading from Excel (as compared to Access which is very fast in .net) is going to be a significant barrier to converting VBA projects to VSTO/.net projects.

// c# code
int iNumberOfColumns = 251, iNumberOfRecords = 2000;
// should be more efficient to read in as much of the Excel data as possible from a range into a 2D Array of objects:
Object[,] array = new Object[iNumberOfRecords, iNumberOfColumns];
Excel.Range thisRange = XLWorksheet.get_Range(objRange.Cells.get_Item(2, 1), objRange.Cells.get_Item(2 + iNumberOfRecords - 1, iNumberOfColumns));
array = (Object[,])thisRange.get_Value(Excel.XlRangeValueDataType.xlRangeValueDefault);  // previously .Value2 which leads to dates and currency excel values being returned as doubles!
 
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// IMPORTANT: for some reason, the array when copied from Excel is 1 based in both dimensions!
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
for (int iRow = 1; iRow <= iNumberOfRecords; iRow++)
{
    int iThisMemberID = pConvert.ToInt32(array[iRow, 1]); // pConvert is an object of a class that I created to handle the conversion of objects to ints, DateTime, etc
    // more code to read in each field (column) value and do something with it
} // for iRow

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