Lol, Arachne is getting hitlocked by coin throwing spam. The real cheat here is him throwing continuously, accurately and quickly.
In-game mechanic exploitation to the fullest.
It's clever and not the typical oneshotting attack from an OP protagonist. I also like how his party members actually had jobs to do to make this strat work. This strat is not something he could've pulled off alone, he'd have been forced to do something else.
Now this normally wouldn't count as pay-to-win if it were still a game, since he's supposed to be using virtual in-game currency and not real cash... but it's technically PTW now because these gold coins are now real money after getting isekai'd to this world.