GOTY always work like that. You paid the premium price to get it before a certain date. That's how it is. If you can't wait around for the GOTY edition, then tough. You paid to have it by a particular time. GOTY are basically the 'sales' pack of games because the high profit period is over and thus the value of the commodity has depreciated so in order for it to be sexy to a consumer, you make huge packs. It's how I got into Fallout. It looked awful to me, then the GOTY came out which had a whole bunch of stuff, so I bought it and now I'm over 500 hours in. GOTY is like dressing a game up in lingerie, it's sexier, dirtier, and I'm drunk right now, apologies.
But I understand, as a fellow inhabitant of Kangaroo land, Origins loves to overcharge us based on demographics. You can be a sneaking willy like me and get a VPN like PIA and by it with a US IP for the US price of $20-ish. I ended up paying $21 for Descent, a wonderful $4 saving!
Or you know, just buy the GOTY edition and maybe gift the main game key (if Origin keys even work like that, I don't know, I bend over for Steam) to someone else. I mean, sure it's $90 (on the Australian one, seriously, VPN and you could save like $10) but buying the DLC separately is already going to cost you $70-80