Magic: The Gathering card singles prices have started off 2021 with a monster sale of a Black Lotus (see "High Grade 'Magic: The Gathering' Alpha Black Lotus Goes for $511.1K") and an uptick of prices of Commander cards on the Reserved List, particularly those from Revised Edition and Urza's block. Revised Edition cards have been on fire lately, particularly dual lands. As an example, Underground Sea was going for about $570 as a market price back at the end of November, and are now listed at $839, which represents a 47% increase (prices derived from TCGplayer listings). The increases on dual land prices vary based on card desirability, but even the least desirable dual land, the Plateau, is up about 30% since November ($200 market price increased to $260).
Reserved List cards from Urza's block, which includes the Urza's Saga, Urza's Destiny, and Urza's Legacy sets, have shot up the singles price charts as well. Commander-staple cards like Gilded Drake, Treachery, and Replenish have all seen solid year-over-year increases in value. As another example, the card Time Spiral, which is in this block of sets, has gone from around $110 to $172 since November (a 56% increase).
The increase in Reserved List card prices can be attributed to a number of factors. Buylist prices and trade-in credit numbers for online singles sellers have been relatively high lately, likely due to a lack of convention buying to replenish inventories, lack of singles coming into feeder stores due to COVID-19 organized play restrictions (no in-store play equals few players around with cards to sell), and an increased customer demand for Commander staple cards to use for at-home play.
As an illustration of high buylist numbers, the Card Kingdom buylist price on a near mint version of Underground Sea is $730 in cash and $948 in credit (as of the publication of this article). The cash number is only about 13% off the market price, where CK buylist prices generally fall anywhere between 40% to 60% off of the market value of any individual card, and the credit number is clearly 13% above the TCGplayer market price. This not an anomaly, either. At least two significant online sellers on the TCGplayer Trade-In market are offering $650 and $726.45 for the same card.
For more information on Magic: The Gathering releases, check out the release calendar (see " 'Magic: The Gathering' Release Calendar for 2020/2021").