I realize Eurogames have been moving away from the mechanic for a long while, but I still love auctions. Age of Steam and Princes of Florence remain two of my four favorite strategy games (joined by Imperial and Race for the Galaxy), and among lighter games, I still love Ra and Medici and No Thanks!, etc.
Have there been any great recent (2015+) auction-centric games? Some people's eyes glaze over as soon as they see a train or Renaissance theme (or merely functional, instead of evocative, artwork).
QE just ended on KS and it's a auction game where you can bid any amount whatsoever (you are 'printing the money' as you go along), all the bids stay mostly hidden, but you reveal everything at the end and the player who printed the most money loses (there are also VPs to win along the way, so there is a winner). It's supposedly a big mindgame.
Container is older (2007) and kind of thematically odd sometimes, but very simple to play, tough to master. Overall just a delicious slice of bidding in a tight closed economy. It also has some nice bid mechanics - one-time blind bid (speeds up the process a lot), and you as the seller can either accept the bid, or pay it yourself and take it.
Ponzi Scheme is another interesting game, from 2015. You are running a Ponzi scheme, so you are free to take a bunch of free cash from dupes every turn, the catch being that you've promised to pay them some pretty crazy interest rates. Meanwhile, you're making secret bids to other players for their properties (the VP in the game), again with a similar mechanic to Container of taking the bid or matching it. It's inevitable that none of this is sustainable, so you're hoping to outpace the first player to go bankrupt.
Finally I'll add
Tramways (2016), which is a streamlined (but still rather brain-burny) train game with a hand building mechanic, lots of fun to combine cards in different ways to do your actions. The other twist to the genre is the way the auctions work, which is that you have to pay each bid you make (even if you don't win). This makes even a 2P auction a bit more interesting. It's also a great solo game, if you're into that.
Also I'll just add that I love Ra, incredible game.