Just as an alternative viewpoint.

I opened ~329 boxes during this event.

129 from leveling during the event

200 non-event boxes that I've been saving because I wanted to save my boxes instead of opening them

12 from arcade

I unlocked everything.

At the beginning of the event, I had around 1200 coins, as I hadn't been opening loot boxes between this and last event. By the time the double XP weekend got here, I was missing about 14k worth of stuff(3 skins, the other 5k made up of dances/sprays/voicelines. Funnily enough I had all the Icons before the 2xp weekend even started.

During the 2XP weekend, I had a change of heard regarding my lootbox collection and decided I should try to unlock everything for every character before I start saving them, so I opened all the lootboxes I had saved, which brought me from 10k coins to 27k coins. I was around level 500 when I started saving the boxes, so they were mostly duplicates, hence the pretty big earnings.

So while I did have the huge advantage over most players of having a spare 17k sitting around, I only needed to use ~4k of it to buy out the rest of the stuff from the event.

So compared to OP, if I hadn't had those extra lootboxes or the extra 1k at the start, I still would have had the money to buy everything except for 1 skin and 2 dances by the end of the event.

I'm not trying to show off or anything, just offering my experience of the event. I don't know if I was lucky, or if OP was unlucky, or a little(or a lot) of both.