Yeah you overpaid. (Assuming American)

Hydroton 10l is $15 on Amazon and 25l is $25

Mother Earth Hydroton Original Clay Pebbles - 10 Liter, Lightweight Expanded Clay Aggregate https://www.amazon.com/dp/B01KYYZ9DE/ref=cm_sw_r_cp_api_i_V2S61BKTTY3HCTXMRS8F

This same brand you bought is like $11 for the same size on another site (and like 22 on Amazon)

https://www.parisfarmersunion.com/HYDROFARM-GROWIT-CLAY-PEBBLES-10L-p/039443.htm

Walmart 3rd party listings are sketchy as hell, and never trust the list price for anything at any time, it’s all marketing.