I don't know why DA2 DLCs are expensive, but DA2 is definitely worth it. During my Codex exile last year i replayed both DAO (+expansion) and DA2, obviously now with a better PC than i had back then, all patched, etc, so i got the full experience this time. I got to say, people who put the original Dragon Age Origins on a pedestal are fucking idiots. It was trash, i FORCED myself to finish it. The first time i played it i ragequited (honestly mostly out of boredom) during the duel with that traitor usurper faggot, i don't remember his name and i don't care. So i still got pretty close to the end of the game. Next time i completed it. Oh boy, what a shitshow. The combat was boring and tedious trash. The story your typical bioware plot they keep using on (almost) every single game. The setting was your typical lord of the rings clone. The graphics were pretty shitty to be honest. It was bland-by-the-numbers-game. The expansion was even worse.
But DA2 was awesome and this time i replayed it in full D3D11 glory (i didn't have a D3D11 gpu the first time). The combat was much more fluid and enjoyable. YES, there were no tactics involved, and that was a plus in my book. DAO didn't have any tactics either, if you are being honest. But then again, people here consider the original Fallout as a tactical game, so.... I enjoyed the flashier spells (yes i roleplayed a mage, the only way you can enjoy Dragon Age series, other classes suck huge black cock) and the faster combat. Still, DA2 is not a combatfag game. Combat just exists, like in the Witcher 3. It was the story and characters that mattered more, and it was leaps and bounds ahead of the GARBAGE that was Origins. It was a somewhat original story attempting to present the evolution of the place and characters during different time periods, and it was a nice change of pace. It had more C&C than Origins did. The graphics were VASTLY improved and i liked the voice acting much more. I loved some of the sidequests too! The only real, honest criticism you can make is the recycling of the maps, but i suppose that was in some ways intended, since you are stuck in a certain place and just the time changes. Still, i don't understand why people complained much, Baldur's Gate 2 recycled maps much more than DA2, and no one complained.... BG2, outside of the main areas, recycled all random encounters and also recycled a lot of the interior areas. Exactly like DA2 did. But i suppose if you are an entitled snowflake and want to bitch about a game, you will find something to nitpick.
All in all, i don't think the Dragon Age series is any good. 1/3 games is good, not exceptional, just good, Origins and Inquisition are overproduced mediocrities at best. If you have to play 1, just play DA2. It is cheap these days and runs maxed on a cheap laptop.