Why not vegan? Not being awkward but I don’t see a reason not to buy vegan.
There’s loads of vit d’s out there. D3 is a superior form over D2. But there’s plenty of cheaper (synthetic) ones out there in Holland and Barrett for example. Whether they’re as effectively absorbed by the body is a whole other discussion. But if you look at the ingredients of the Together ones there are only 4 which are all natural / from natural. If you look at the ingredients of a typical cheaper synthetic one it looks something like this:
Bulking agents (microcrystaline cellulose, maltodextrin, modified starch, vegetable oil), anti-caking agents (vegetable stearic acid, silicon dioxide, vegetable magnesium stearate), glazing agents (hydroxypropylmethyl cellulose, glycerin (from rapeseed oil), hydroxypropyl cellulose), colour (riboflavin) vitamin D3 (cholecalciferol).