It's not really a surprise, but DJI's stock filters are really expensive. If you're like me and didn't get the Mavic 3 as part of a kit with filters, but still need some, I'd suggest checking out PGYTECH's. There's a lot of brands out there, but I recently had the opportunity to test out their model, and I was pretty happy with them. There's more details in my full review here, but they're a good value, with no image quality issues. The included case is a nice bonus, and the UV model is perfect to have as a backup in case you scratch or lose your stock DJI clear filter. I've not tested out freewell's yet, and Polarpro's special FX filters don't really appeal to me as I'm primarily shooting photos, but I did have the chance to run PGYs against some DJI filters a friend had, and there's not a significant difference between them.
More broadly, I just don't know if I love the experience of using filters on drones - I get that NDs are important for preserving the shutter rule on video, but for stills, I've not found that I "need" a filter. Between having to mess with DJI's weird mounting mechanism and having to land just to swap them out, I'd really try and just make the edit in post. Do you have an essential use for filters beyond ND's?
More broadly, I just don't know if I love the experience of using filters on drones - I get that NDs are important for preserving the shutter rule on video, but for stills, I've not found that I "need" a filter. Between having to mess with DJI's weird mounting mechanism and having to land just to swap them out, I'd really try and just make the edit in post. Do you have an essential use for filters beyond ND's?