The gold statue thing makes Lewis look pretty bad... but I think it's not nearly as bad as it seems.

• There's a lot that implies that the planet Stardew Valley is set in isn't Earth--not least because the Globe decorative item doesn't have the same continents as Earth. This means that we could be on a different planet with different levels of gold deposits.
• Your farmer, with a moderate level of skill and a hand pickaxe, can easily get gold out of the local mines. So can Clint; and it can be panned out of the water, too. But there's no gold rush; in fact, nobody thinks this is particularly unusual. People even throw out gold nuggets occasionally.
• Gold is used for all kinds of things we don't use it for in the real world, including completely ordinary things like sprinklers, seed extractors, and even fishhooks. It's also used in solar panels--in the real world, solar panels made with gold are expensive and reserved for things like being sent to space on satellites.
• If you find ore that contains gold, you can sell it for 25g--half the price of a can of soda. Or you can buy it off the blacksmith for 400g, the price of a mug of beer at the local tavern. Smelt it, and you can sell five pieces of ore (one bar) for 250g.
• So... just how much did that statue cost Lewis? Probably not nearly as much as it seems. It's still a lot of gold--but it's nowhere near a fortune. At the moment, a standard gold bar, weighing 12.4 kg, is worth about $720,000 in real-world dollars. And a mug of beer, if bought at a bar--one assumes Gus sells high quality beer, and marks up the price to make a profit--costs about $8. That means that gold is about ninety thousand times less valuable in Pelican Town than it is in the real world. In fact, for Pelican Town, gold is worth about one-tenth as much as copper is in the real world.
• If Lewis lived in the real world, wanted a statue of himself, and used the same level of resources as he did in Pelican Town, he would be able to buy the materials for only a two-foot-tall copper statue.

Is it still bad that Lewis is building statues of himself? Sure; it's a sign of vanity, and if he's using tax money to build it, it's a waste of resources. But it's not exactly the extreme breach of the public trust that it would be if gold were worth as much there as it is here.