I was watching Sky News (UK) last night. In one program (I am not able to now find the link on Youtube) their defense analysis, Professor Michael Clarke, stated that the new Iranian low-tech delta wing “kamikaze” drones cost only $20,000 (see: HESA Shahed 136 – Wikipedia) while the Russian SS-21s cost $300,000 (see: OTR-21 Tochka – Wikipedia). I have no idea of the accuracy of those figures, but Wikipedia does state that the cost of an SS-21 is 0.3 million, based upon this article: Over the weekend, Russia fired missiles worth about $200 million at Ukraine. Forbes  score; — Forbes.ua. It gives the cost of the various Russian missiles as: “…the cost of the X-101 rocket was $13 million, the Caliber was $6.5 million, the Iskander was $3 million, the Onyx was $1.25 million, the Kh-22 was $1 million, and the Tochka-U was $0.3 million.” Wikipedia gives the price of each HESA Shahed 136 as $20,000 to €50,000. Its two referenced sources are: Iranian ‘suicide’ drones: Russia’s new favorite weapon in Ukraine war | International | EL PAÍS English Edition (elpais.com) and Financial toll on Ukraine of downing drones ‘vastly exceeds Russian costs’ | Ukraine | The Guardian. The two articles also state that Russia has ordered 2,400 of these drones, based upon a statement made by Zelenskyy.
The obvious implication is that Russian can fill the skies with these inexpensive low-tech drones, and even if 80% or more are shot down, enough will get through to cause damage. Is this the driver in the new Russian bombardment strategy?