The answers to the OP’s questions are overly cynical in my opinion.  I get the annoyance with GW.  I had parted ways with GW for 13+ years before KT’18 brought me back (and Underworlds kept me a customer).  KT’21’s ruleset is surprisingly good, one of the best I have experienced (better than Stargrave or Starbreach, and certainly an improvement on KT’18 where the game was mostly won at the list building stage and where a faction’s basic trooper barely impacted the game).

I wouldn’t let the buy-in issues, such as they are, put you off Osbad.  Here is what I have suggested to others:

Buy the Rulebook;

Buy the Compendium if you need rules for more than 1-2 factions, otherwise just use the Battlescribe app or carefully watch video reviews of the book (like Glass Half Dead’s vid) for the info on your faction.  If your one faction is either Imperial Guard or Orks, then skip the Compendium and buy the Octarius book on eBay come Aug. 28th;

Buy the essentials pack if you can’t be bothered to come up with alternatives for the counters and the 6 barricades (2″ x 1″, these are necessary).  The measuring tool is unnecessary, just use your measuring tape;

Buy the TacOps card pack unless you want to make your own (these secondary objectives are listed in the rulebook, so one could print them onto heavy paper and sleeve them).

A few targeted rebuttals…

Blinky465 – You mischaracterize TM’s opinion on KT’21.  He was disappointed with the Compendium.  He liked the ruleset, even if he had issues with certain aspects of it (like the lack of a morale phase, though much of it irrelevant to gameplay, such as the measurement symbols and terminology).

Slayerofworlds – The Compendium has been stated by a few reviewers to provide competent army lists that are balanced even against the two Octarius forces.  Yes, they lack the load of specialist operatives with their bespoke special rules but these Compendium lists are not subpar forces.  And they may not be superseded by the release of a faction’s bespoke team.  I could see a Tyranid release that is nothing but genestealers, perhaps with a lictor.  A Tyranid player might not be enamored with genestealers (I, for one) and would continue playing with a warrior/gaunt force from the Compendium.