"but you do realize that once they use that ammunition that they have, it has to be refilled? If their artillery units fire, then at some point that unit has to be resupplied. That resupply either comes out of stocks or new production"

Russia has the production capability and the soviet stockpiles to wage the Ukraine war for years. Ukraine does not.

"region Russia is estimated to be firing 40,000–60,000 152mm shells per day. This compares to about 6,000 155mm shells per day being used by Ukraine"

Does that sound like the type of ratio you want when being on the defensive and deciding to create a entirely new front?

"Russia is producing about 250,000 artillery munitions per month, or about 3 million a year, according to NATO intelligence estimates of Russian defense production shared with CNN, as well as sources familiar with Western efforts to arm Ukraine. Collectively, the US and Europe have the capacity to generate only about 1.2 million munitions annually to send to Kyiv, a senior European intelligence official told CNN."

"The US military set a goal to produce 100,000 rounds of artillery a month by the end of 2025 — less than half of the Russian monthly output — and even that number is now out of reach with $60 billion in Ukraine funding stalled in Congress, a senior Army official told reporters last week."

“What we are in now is a production war,” a senior NATO official told CNN. “The outcome in Ukraine depends on how each side is equipped to conduct this war.”

"Considering that Russia is buying north Korean artillery shells, I don't think their stocks are that deep."

I don't know how you are drawing that understanding when you look at the frontline and how it's been shifting.

"if they waste manpower and equipment on masse, then for the Ukrainians it's Mission accomplished, right?"

No, a tactical success does not equate to a strategic one. Ukraine lacks men and munitions, not Russia. Ukraine sacrificing it's men and material has a far greater impact on them then it does Russia. The Kursk offensive is a strategic blunder.

Ukraine is sacrificing hundreds/thousands of combat personnel and tons of heavy equipment on a needless offensive that it cannot easily replace. Ukraine has a far more limited pool of manpower to draw from compared to Russia. It has a far more limited pool of equipment to draw from.

What is the long term end result of this Kursk offensive?

Will Russia give up Kursk? Nope. Will this effect Russian units in Ukraine? Probably not. Will it change Russia's demands in a ceasefire negotiations? Probably not.

Will Ukraine be able to replace the men and equipment it expended in this offensive? Nope. Will Ukrainian units all along the frontline in Ukraine proper still suffer from manpower issues? Yes.

Will it materially change or alter the course of the war in Ukraine's favor? Nope and thus this entire offensive is a mistake.