I've now played Mercado three times on a review copy from Thames & Kosmos, the North American branch of KOSMOS, ahead of the game's U.S. debut at Gen Con 2018 in early August, and now I have an understanding of what the game is and how it works. Amazing how that happens! Did I read the back of the box or overhear someone else talking about the game, or did I actually put the bits in my hand and live through it? Night and day!
That said, I'll now attempt to convey the game experience to you, both through the video below and this short explanation: In Mercado, you're in an arms race to buy stuff as quickly as possible. You want stuff to show others how prestigious you are, and to pay for this stuff you need to lay out the right coins to buy it. Strangely if an item says that it costs three silver coins, you can't pay for it with three gold coins instead. Three silver! It says so right on the sign!
Each turn you dig into your purse for three coins — five if you can discard a seal, another showy sign of your ostentatious lifestyle — then you place those coins on one or more things that you want to buy. Yes, you're making down payments as you window shop. Whoever lays down the right coins first gets the item, along with its associated points and any benefit or penalty shown on the tile. Whoever else had coins on the item returns those coins to their purse, with the player who was closest to buying it receiving a complimentary seal. You tried to show off your wealth, and we appreciate the effort. Better luck next time.
Whoever bought the thing must place their coins on their character tile, and instead of digging for coins on a turn, you can dump all spent coins back in your purse. I suppose this represents the interest gained from the inheritance that uncle bequeathed you in 1909, with you receiving back exactly the coins you spent, along with any counterfeit coins that came out of your purse but could not be spent. Yes, you have junk coins in your purse and instead of throwing them away like a smart person, you keep them in pocket to jingle like a frivolous dandy, setting them aside whenever you draw them out because you know that merchants would shun you should you try to spend them.
In effect, Mercado is a racing game played out in turns. You want reputation to win, and to gain reputation you need to buy things, and to buy things you need to lay out the right coins, but will you draw those coins before other players can? Sometimes you press your luck, placing all your coins on a bracelet that you can almost buy, hoping that no one else can snatch it from the store before you, and sometimes you spread the coins around, or you visit one of the two merchants to gain privilege or magic money from them. More bonuses and penalties await on the reputation track, which might inspire you to buy something you otherwise wouldn't touch. To quote one of my fellow players: "Those shoes are hideous, but three points are three points."