Fun fact: Back when I played FF13 I played, as I do, with the aim of unlocking all the trophies in it. There's a trophy for having owned every weapon/accessory. You don't need to have them all at once, you just need to have had them at some point. I didn't sell anything as I played through the game, with the idea that I'd unlock the base versions of everything then work on upgrading them all once I'd reached the endgame. I had the strategy guide for the game, so I ticked them off the list in that as I got them all.
I didn't actually get around to cleaning it up until years later. I tried to work out how much money I needed and what was the quickest way of getting it. The weapons in particular were annoying because each character had eight different weapons that you had to upgrade and each of them needed a different amount of XP put into it and then a different component to finally change it into the new one. Plus each character had a 3rd stage "Ultima Weapon" which needed a special catalyst which you could only get by fighting one of the insanely strong turtle enemies which you basically needed fully upgraded gear for anyway.
Going by my posts on the internet at the time it took me around 30 hours to grind for all of this stuff after spending ~95 hours getting to that starting point, although I had over-levelled in a few places in the story just to make sure I could get through without too much stress. I miscalculated how much money I needed to get all of the things I needed and I was getting bored so I was selling stuff to try and speed up the process and that just made it worse.
I had the vague notion of finishing the game before the end of 2017 so there I am on Hogmanay, having finished work and gone home to finish the last couple of things I needed. The trophy didn't pop as soon as you got the last item, you had to go and see someone to unlock it. I went and talked to them and you probably know where this story is going by this point. No trophy. I didn't know what I'd missed.
Luckily I'd kept a few different save files in case anything went wrong so I was back to the beginning. I spent the first week of 2018 running along a corridor near the end grinding two battles over and over. I started watching Zero Punctuation from the beginning again as I was playing, I went from ~2008 to 2012, just watching one video after the other. An extra 30 hours for that.
Maybe one day I'll play them again (oh yes, I've also finished 13-2 and 13-3) if I take leave of my senses. The music from 13 is genuinely brilliant throughout, however: