Armchair Traveller :(
My dad constantly suffers from back pain and prefers sleeping on high density foam mattress. If the pain is more, he sleeps on floor for a while, so I believe that hard surfaces are better for back but I never had any such trouble on my custom built mattress which is pretty soft.I spent 34 K on a spring mattress, only to sell it for 2.5 K after 5 years. Went back to coir + foam combination which is best for back support. The ones you get in hotels will be even more expensive.
I checked on amazon and found a few options with 8" & 10" thickness for under 21k which I feel is great.
8" .... https://www.amazon.in/gp/product/B07141VLY2/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A2YL4DG8STMIG0
10" .... https://www.amazon.in/gp/product/B078J2433Q/ref=ox_sc_act_title_3?ie=UTF8&psc=1&smid=A1LOIS1UQSAB8S