Google-sheets – Comparing cell value 450-500 to another cell of value 475 in Google Sheets

The match formula will tell you which column within 1:1 matches today(); in conjunction with index we can use that column number to get the address of the cell holding the Yes/No data for today. This becomes useful when paired through string concatenation (&) with the address of the first cell of the Yes/No data ($A$2 here) -- the 'dynamic' range you wanted can now be interpreted using the indirect formula!

All together, you're looking at the following formula for B3 in your example:

=COUNTIF(INDIRECT("$A$2:"&CELL("address",INDEX($1:$2,2,MATCH(TODAY(),$1:$1)))),"Yes")

edit

I temporarily forgot about filter, which makes this task much easier: =COUNTIF(FILTER(2:2,1:1<=TODAY()),"No")

I do not know how to solve this problem without scripts, but there is a simple work around. When you update prices, you can drag them elsewhere in your sheet (e.g. below, in the form of a price record). The values on the 'Sales' sheet will stay linked to the original price, and the formula you enter for sales will be the same.

If you choose this work around, I would recommend creating a script that automatically moves your prices so that you don't have to manually drag things around and so that the newest prices appear closer to the top. There are many ways to make that type of script, but here's one not so elegant, but simple way:

var ss = SpreadsheetApp.getActiver();

// Many of these values depend on the layout of your document.
// I have indicated where you will need to change values if
// you change the layout.

function onOpen(){
  // This will make a menu appear that allows you to run the scripts
  var ss = SpreadsheetApp.getActive();
  var items = [
    {name: 'Make space for a new price', functionName: 'newprice'},
    {name: 'New sales day', functionName: 'newsales'},
  ];
  ss.addMenu('New Entry', items);
};

function newprice(){
  // This will simply insert a row under your prices.
  // You just have to drag the on you want to change into the new row
  // Your info on the other sheets will stay linked to the correct number
  var sheet = ss.getSheets()[1]; // This number may need editing
  sheet.insertRowBefore(7); // This number may also need attention
};

function newsales(){
  var sheet = ss.getSheets()[0];
  var where = 7;  // Where to add the new lines?
  var how_many = 5;  // How many products to add?
  for (var ind = 0; ind < how_many; ind ++){
    sheet.insertRowBefore(where);
  };
  // Copy the values
  var source = sheet.getRange("A3:G7"); // This would need attention
  var destination = sheet.getRange("A8:G12");  // And this...
  source.copyValuesToRange(destination,1,1,1,1);
};

Using a script may be more trouble than it's worth for this type of problem.

If for some reason (I can't imagine why) you want to have one cell that adds old prices and new prices, then you need a more advanced script. It would be easier to make one cell associated with each price, and then add them in the final cell.