As others have stated, the issue is that you're apparently thinking incorrectly. You're not buying anything again, you didn't own what you're needing to buy in the first place. You owned the license on the Xbox 360. That doesn't entitle you to anything on the Xbox One. Even the freebie upgrades that were offered previously for the first 2 expansions and the time-limited freebie upgrade for the base game were done entirely by Bungie's choice; they did it out of the goodness of their leads' hearts because at the time those upgrades were put in place, the console generation had just moved forward so there were still a lot of people who had just bought the game and then got a new system shortly thereafter. So, get it out of your head that you're buying it again, because you're not. You never owned the Xbox One license for the TTK content, so you're buying absolutely squat all over again. You're paying for something you feel you already paid for, even though you didn't. Even Bungie had to pay for rating and store licenses separately for each version of the game. I hope that helps with your understanding as far as why buying the new license is something you need to do.

You should be eligible for destiny the collection upgrade. https://www.bungie.net/Mobi/en/About/Article?id=12122

TDB and HoW were included in a special program that allowed them to transfer to next gen free of charge. TTK and ROI are not included in such a program. It is actually normal that you have to by the next gen version of the same game if you change console generations. You only bought the license for the 360, not the XB1 If you are wanting ROI as well as TTK, your best bet at this point is to simply buy Destiny: The Collection.

No, your saved progress with transfer 1 time but you must repurchase the content.

Only house of wolves and dark below transfer. Taken King and preorders/collector editions do not And the base game only transfers if you bought it digitally before Jan 2015