The price comparing with the exchange rate of the time I purchased? In other words, the price in BTC or the price in BTC/USD?
If you mean the first one, then I can view my transactions on a block explorer, such as
Blockchair, but you should note that the explorer will know what you're looking and thus, you may ruin your privacy. There are other ways to view your transactions too such as setting up your own
Electrum server, that would require running your own
Bitcoin node, but I won't keep going, because I don't know how familiar you are with these terms.
If you mean the second one, just create a spreadsheet and write your spent bitcoins along with the exchange rate it had when you made the purchase. On a third table, you could have the sum.
Example:
|
|
Edit: On Blockchair you can see the transaction value in USD of the exchange rate the time it was broadcasted. This is an example of Hal Finney receiving 50 bitcoins in 2009: