AITA for not telling my MIL that I bought her birthday gift for cheap?

I (28F) bought my MIL (70ish F) a birthday gift for under $20, and she absolutely loves it. It’s a funny mug that says “I’m not old, I’m COVID years old, which is like 5 years for every one year.”<br><br>She showed it off to her sister, her friends, and even to the mailman. She was so excited to tell everyone that her DIL bought it for her, and she was so proud of it that she even did a photoshoot with it and posted it online. My husband and I are thrilled that she loves it. It’s the first gift I’ve ever bought her that she actually likes.<br><br>Now, I’m worried that she’ll find out that I only paid $15 for it. I feel like she’s going to be upset to learn that it was so cheap. I’ve never purchased a gift for her before without her complaining that it was the wrong thing or the wrong color or that I should have spent more money.<br><br>AITA for not telling her how much the mug costs? Should I lie to her if she finds out that it was cheap? I would prefer not to lie to her, but I also don’t want to hurt her feelings by telling her the truth.