You can get 15 kWh for $1,3000 if you pick up in Texas (these use EVE MB31 which usually end up testing at ~310 Ah): https://www.apexiummall.com/index.php?route=product/product&...
It just keeps getting cheaper and cheaper every year...
I am also in the EU and last year I have purchased a YIXIANG DIY battery case and 16 EVE MB31 cells for a combined cost of less than 2000 EUR without VAT.
It was shipped from China so I had to wait ~2 months to get it which is a disadvantage. Local warehouse stock was slightly more expensive.
What 13000? Here in the EU we pay around 3-3.5K for 15 kWh.