Rosewill 4U Rackmount Server Chassis | Supports up to 24 3.5" 12Gbps Hot Swap SATA/SAS | E-ATX & SSI-EEB Compatible | 3X 120x38mm PWM Fan | RSV-H424

This is about 400€ in EU: https://www.inter-tech.de/productdetails-142/4U-4424_EN.html . I see another similar product is available for similar price on Amazon: https://www.amazon.com/Rosewill-RSV-L4500U-Thickness-Rackmount-Server/dp/B0FZ2S9YJG?th=1&psc=1. Note that for 24 HDDs you probably want a case that fits CRPS/server PSU.