Since the Kharkov incursion Russians seem to take larger swathes of lands, the size of square kms, at least weekly, but lately every day, elsewhere than the Kharkov front, down at Siversk, Bakhmut, Avdiivka and Donetsk front. So essentially the Kharkov front sucks the resources from elsewhere and this allows Russians to advance.
It is possible that Ukrainian started to trade more land, to preserve life and material. Frankly these patches they withdraw from has nothing on them, ruins at best.
They really have to pick where they allow the enemy to advance, because the road from Pokrovsk to Kramatorsk is vital.

I heard today that a plain 155mm NATO shell costs 8 times more per round than the Russian counterpart (152mm). I tried to find a source, but gave up fast to get a more recent, so here's two older.
From 2023 November:
https://www.defenseone.com/business/2023/11/race-make-artillery-shells-us-eu-see-different-results/392288/
>In October, NATO’s senior military officer, Adm. Rob Bauer, said that the price for one 155mm shell had risen from 2,000 euros ($2,171) at the start of Russia’s full-scale invasion to 8,000 euros ($8,489.60).
>For comparison, the U.S. currently pays $3,000 for its most modern shells, according to an Army spokesperson. That price includes the charge, fuze, and shell body.
From 2024 May:
https://news.sky.com/story/russia-is-producing-artillery-shells-around-three-times-faster-than-ukraines-western-allies-and-for-about-a-quarter-of-the-cost-13143224
>On cost, it said the average production cost per 155 mm shell - the type produced by NATO countries - was about $4,000 (£3,160) per unit, though it varied significantly between countries. This is compared with a reported Russian production cost of around $1,000 (£790) per 152 mm shell that the Russian armed forces use.
The first article is closer to what I heard.