It's pretty clear from the moment we meet them that the Salt family is rich, and that plays a big role in why Veruca finds the Golden Ticket. Mr. Salt tells everyone just how he used his money to make sure his daughter got what she wanted: "As soon as my little girl told me that she simply had to have one of those Golden tickets, I went out into the town and started buying up all the Wonka bars I could lay my hands on. Thousands of them, I must have bought. Hundreds of thousands!" (6.8)
So we know they have enough spare change to spend on hundreds of thousands of chocolate bars. We also know that Mr. Salt has a factory, because he makes all his workers unwrap Veruca's hundreds of thousands of chocolate bars until one of them finally finds the Golden Ticket. Seems like ridiculous waste, but hey, Veruca wants what she wants.
No Sugar, No Spice, Nothing Nice
You know that saying, "Money can't buy everything?" Well, the Salts missed that memo. Money bought them the Golden Ticket, and Mr. Salt is pretty sure it can buy them an Oompa-Loompa and a squirrel, even though they're not for sale.
As for Mrs. Salt, well, she's a lot like her husband, in that she spoils Veruca, telling her "Mummy'll get you a squirrel just as soon as she possibly can." In Chapter 16, we learn she's a geography teacher, and a bit of a know-it-all when she tells Mr. Wonka that "There's no such place" (16.3) as Loompaland (despite the fact that a bunch of Oompa-Loompas are staring at them).
All in all, these are not likeable folks, and the Oompa-Loompas seem to think they are just as bad as their awful, greedy daughter. When they sing their farewell song to Veruca, they blame Mr. and Mrs. Salt for their daughter's behavior, singing,
Who turned her unto such a brat?
They are (and this is very sad)
Her loving parents, MUM and DAD.
And that is why we're glad they fell
Into the garbage chute as well. (24.67)
Apparently, the awful Salts got just what they deserved.
Oh, and one more thing. For an interesting tidbit on the Salts' last name, check out "Tools of Characterization."