Inka - The law is the law, and you can't rationalize breaking it based on personal economics, or whatever. Try getting away with smuggling marijuana, based on it being almost free in Mexico, and quite expensive in the U.S. "Oh, this pot is very expensive in the U.S., and it's for my own personal use. I don't intend to sell it, I promise". Well, not really the same because oranges are legal in the U.S.
The warning signs about crossing restricted agricultural products are very visible. They prevent using ignorance of the law as an excuse. The reasons for restrictions vary, depending on the particular fruit or vegetable. In any case, the undeclared restricted items will be confiscated, if found, and you can also be subjected to significant fines, at the discretion of the inspector. You will not be subject to sanctions if you declare something that happens to be restricted.
Restrictions based on preventing the spread of disease to our domestic crops are easy to understand and accept. Oranges fall into this category, preventing the spread of "quick decline" virus, and other diseases that are a threat to our domestic citrus (orange) industry. Sounds good, but the actual "threat" may be more of a myth than reality. However, other types of citrus aren't restricted.
Other restrictions are based on economic reasons. I believe avocados are an example. Avocados can be imported if the pits are removed. This makes no sense from a disease prevention aspect. Removing the pit makes the fruit rapidly perishable. The same applies to importing coconuts. They can only be imported if the milk is drained. Try to find an inspector who can explain the reason behind this.
Many importation restrictions may be no more than nonsense, and we may not agree with them. However, getting caught violating them may cause one to get flagged for secondary inspection on subsequent border crossings.