It seems like there are two effects we're considering at the same time:
1. UBI might increase people's willingness to pay for goods in general, and the prices of goods that are most strongly driven by willingness to pay would rise. (Rent in expensive cities might be an example of this. Milk, soap, and socks probably aren't.)
2. To the extent that UBI is paid for with higher taxes, the prices of everything would go up. This seems obviously true on average and to some extent, but the specific numbers matter a lot. For example if prices go up by 10%, but the people whom UBI is designed to help see their income rise by 20%, then UBI is achieving its stated goal. (Importantly, the hypothetical 10% rise in prices doesn't reflect wealth being burned or spent, but rather resources being moved around in some sense.)
1. UBI might increase people's willingness to pay for goods in general, and the prices of goods that are most strongly driven by willingness to pay would rise. (Rent in expensive cities might be an example of this. Milk, soap, and socks probably aren't.)
2. To the extent that UBI is paid for with higher taxes, the prices of everything would go up. This seems obviously true on average and to some extent, but the specific numbers matter a lot. For example if prices go up by 10%, but the people whom UBI is designed to help see their income rise by 20%, then UBI is achieving its stated goal. (Importantly, the hypothetical 10% rise in prices doesn't reflect wealth being burned or spent, but rather resources being moved around in some sense.)