Masterwork cores drop very frequently from many sources now - vendors, rank ups, deleting weapons / armour etc. Its not hard to get 10 quickly to convert to a prism. Prisms drop fairly regularly from Crucible when you have the mod on the ghost for precision kills. I generally get about 3 or 4 in a few hours session. Its easier than ever to obtain cores / prisms / shards. I started this season with no masterworked armour and only a few prisms and masterwork cores. I have never bothered at all masterworking to the top level any armour previously and never had a shard on my inventory. I now have every armour piece masterworked and 6 shards in the bank ready to go. That isnt through playing that much either - maybe 10 hrs per week. I dont really PvE apart from doing the bounties from the gunsmith each time im on and just crucible for the rest.

Unless they lower the cost to masterwork armor or add prisms to more activities this makes sunsetting armor worse than it is.

You can literally do it then level it up like once and dismantle it for a couple of prisms