alt Hacker News50-75% off of AAA games from that year were not uncommon. I don't think the sales have ever really been comparable ever since. There are people who have put together Wayback machine compilations to compare - I just took a look at the 2014 and 2015 deals (refunds were ~ 2015) and there was a remarkable drop-off in the sales and variety of games at deep discount.
I think more importantly for Valve though - the daily flash sales were incredibly important to drive engagement and grow their presence.
I think the "why didn't Valve offer refunds before" is kind of revisionist. It wasn't clear that refunds were even a necessary component of cheaper digital games at the time.
Replies
You could get entire publisher catalogues for peanuts. I think at least half my steam library is useless filler because I bought every game WB ever published for $40 to get the new batman game or similar.
I think one precursor could have been EA's debacle with Sim City in 2013, when they apparently had a huge wave of disappointed customers doing chargebacks. I'm not aware of any public statement/evidence of this, but it really wouldn't surprise me if their payment processor leaned on them to provide a better means of accomplishing that, and it gave them a way to portray their store as customer friendly.