Could have been disappointed - is that a correct usage of could have been?

It is to my understanding that 'could have been' talks about a possible present situation that have not happened but is possible in the present and should be followed by a verb in a continuous form. In the context of - "I'm glad I have bought the product before the sale because the price is worse now. If I didn't buy it back than, I could have been disappointed." - am I using could have been correctly?

Solution 1:

No. Could have been refers to a possibility that existed in the past. "If I had not had my umbrella with me when it rained yesterday, I could have got very wet."

You are glad you bought the product before the sale. If you had not bought it then, you could be disappointed now because the price is (presumably) higher.