If you want to see the price you paid for a token or tokens, say to compare with its current value, you can do so via a block explorer. The price information for transactions seen on a block explorer covers both the current values of a specific transaction but also covers the value on the day of transfer.
You can see this detail using Etherscan.io by looking at the transaction in which you bought the tokens.
The price that is displayed in Etherscan has 2 levels of detail :
- Displaying current value
- Estimated Value on Day of Transfer.
You can toggle between these two by clicking directly on the price that is displayed.
This works for transactions that were already successfully executed on the network.
We recommend that you look at the price that appears next to the full token balance that was transferred between sender and receiver in order to see the exact price (as shown in the above snapshot).