Much like my script to Download Steam Library List, I created a similar script to download your list of Steam Purchases as a CSV file.
It's not perfect because you'll have to filter out the refunds and other types of transactions. Someone on reddit requested me to make it and I figured it was something I wanted to do myself so I did.
Then be sure to click on "Load More Transactions" at the bottom until it disappears so that you will capture your entire history. Then copy-paste the script into your console (hit F12 and "Console" tab).
a=document.createElement`a`;a.href=URL.createObjectURL(new Blob(["Date,Items,Type,Total,Wallet Change,Wallet Balance\n"+[...document.querySelectorAll('.wallet_history_table tr > td')].reduce((p,e,i)=>(p[i/6>>0]=(p[i/6>>0]||"")+'"'+e.innerHTML.trim().replace(/<\/?[^>]+(>|$)/g,"").replace(/\s+/g," ").replace(/"/g,'""').replaceAll(" Remove ","")+'"'+(i%6==5?"":","),p),[]).join`\n`],{type:"text/plain"}));a.click(a.download="steam-purchases.csv");URL.revokeObjectURL(a.href)This script basically takes the HTML table an extracts the cell data and puts it all into a CSV format and downloads it.
It's not great because refunds and steam market sales are positive values so you'll have to manually delete them. I could possibly do that in the code but I don't want to spend more time on this.
If you're curious, my purchase total is $1,454.49 which includes purchasing the Steam Deck OLED for $678.
Let me know if you'd like a script to do this for any other pages!