The Empires games were honestly, for a long time, the only Warriors titles I played. It wasn't really because I didn't like the main ones- always been a big fan, but I'd usually get into the numbered entries a year-ish after they were already released which basically meant that XL and Empires were there, so I'd just nab the latter. Even looking back and thinking that, in DW, I went 2->3->5E->6E->7E-4->8->8E is a bit weird.
Backstory aside, are they worth it? Uh...hard to say, because they kinda all have their own flair and spice. Like, for instance, the big thing about Dynasty Warriors 4/5E and SW4E was that you didn't really control a single character, but your entire Kingdom. It's basically like a very, very lite Romance of the Three Kingdoms (the game series) but it's a hell of a lot of fun even if it can be a bit repetitive. Dynasty Warriors 6E kinda changed things up by introducing the freelancer, where you'd basically choose one officer in a kingdom to play and you were able to even leave kingdoms. This added a fun little dynamic where you could meet people, create your own little squad and either covertly help/hinder kingdoms that were at war with each other, raise your own flag, etc. Sadly DW6 was a mess and so was its Empires title, and I'd say if you're interested in it at all, 7's probably the best of them, with 8 not far behind. But if you want to keep on the SW train 4E's really fun. I don't know if I'd say it's as good as 4 itself considering that game absolutely nailed mission structure, but it's still a good title if you did enjoy 4.
Aaaaand I'm going to say because I could literally go on for hours about anything Warriors related. ESPECIALLY the Empires titles because no one ever talks about them and I'd be the loudest goddamn advocate I could be. I generally get immersed in them so it's really easy for me to play them for long periods of time, they're just good fun, and I know a fair few fans that surprisingly do the same, but I'd say for you, just give one a try and see how it catches your fancy.
And yeah, that's kinda how I am, too. For some reason console games have no idea what the hell price depreciation is. I'm not gonna say that your game needs to drop in price overtime because it's worth less, but I'm also not going to pay 60 bucks for Tales of Vespiria digitally just because I can't find it in goddamn stores. I mean, it's really on you guys if you want lost sales.