There's a problem with this formula.

SergeiBaklan 

Hi Sergei

I had used the problem to challenge my thinking using the newly available LAMBDA functions.

I did also create a recursive formula, based upon a rework of the Fibonacci recursion spreadsheet.  There must be times when I irritate members with my alien solutions and I felt that a recursive solution was a couple of steps too far here.  However, to prove it exists

= TotalCSV(ItemCosts)

where TotalCSV refers to
= LAMBDA(residual,
    LET(
      n, IFERROR( FIND(",", residual), 1+LEN(residual)),
      item, VALUE(LEFT(residual, n-1)),
      reduced, REPLACE(residual, 1, n+1,""),
      partialSum, IF(reduced<>"", TotalCSV(reduced), 0),
      partialSum + item )
    )(ItemCosts)

I offer apologies for those who will not be in a position to evaluate such methods, and may not be for many years.  We seem to have reached a point where Excel 365, though it can run legacy spreadsheet solutions, is actually an utterly different platform which supports a programming approach to solving problems.  When and whether the two strategies will ever come together once more, I am not so sure.