I think the next DLC should be free. When the game came out it was $60 yet for the amount of content it had it should've cost anywhere between $30-40, though I will cut them some slack because their game fell apart while during production. The DLC being released was set at $20 a piece but they never really told us the exact amount of content that was going to be available. Again for TDB and HoW we were kinda screwed over, the content created besides the raid and prison of elders was pretty quick and boring. The DLC should've been free updates. Then the O'Glorious TTK came out, which was a step in the right direction but it wasn't really worth another $40 which should have been $20-30. At that point the loyal players had spent anywhere from $120+. I won't include Microtransactions here because purchasing that is totally up to you *cough*emotesareoverpriced *cough*. By now they should've gotten enough money to make us a TTK sized DLC and if they give it to us for free the community and bungie would be even in terms of the content we paid for.
I bought each dlc on 360 and TTK collector's edition on the one. I'd love it to be free but if it looks good and is under 30 I'll get it.