Update Azure table storage entity except one property - azure-storage

Question

Requirement is up insert 10k records at time and avoid the one property.
When ever I am doing insert or merge it's overriding the existing property which is already process and updated in the entity.
Scenario :
We will receive records from API in the below format
{Name : "Item1-Test1","Color":"Blue"}
{Name : "Item1-Test2","Color":"Red"}
{Name : "Item1-Test3","Color":"Yellow"}
{Name : "Item1-Test4","Color":"White"}
We will add cost property while storing the in Azure table storage below (using for)
{Name : "Item1-Test1","Color":"Blue", Cost :"0"}
{Name : "Item1-Test2","Color":"Red", Cost :"0"}
{Name : "Item1-Test3","Color":"Yellow", Cost :"0"}
{Name : "Item1-Test4","Color":"White", Cost :"0"}
The cost column is processed in code and will be updated based on the requirement as below
(querying cost = 0 and updating the records )
{Name : "Item1-Test1","Color":"Blue", Cost :"100"}
{Name : "Item1-Test2","Color":"Red", Cost :"250"}
{Name : "Item1-Test3","Color":"Yellow", Cost :"100"}
{Name : "Item1-Test4","Color":"White", Cost :"1000"}
We might receive same entity again if we hit the API again. So we are manually manually query the each row to verify that record exist or not in the Azure table and we updating updating the properties other than cost.
As we are receiving more record around 10k to 100k.The verification is consuming more time while insertion.
Challenge faced:
If we skip the cost property while inserting entity newly, we are not able query on the records.
If we add the cost property while inserting it's overriding the existing cost value.