Your buylist price is normally calculated rather than set per card, though you can pin an individual card to a price of your own (see step 7). It starts from the card market value and then applies your Buylist Price Config settings in this order:

1. Market value lookup. The starting point is the card market price from the sources you configure. You can set up to four source slots per game (Primary, Fallback, Final Fallback and Doomsday), and choose from TCGplayer, TCGplayer SKU, CardMarket, CardTrader in USD or EUR, ManaPool (Magic only), Card Kingdom (Magic only), and PriceCharting (requires the PriceCharting add-on). Each slot also has its own price points and fallbacks (market, mid, low, high), and if a slot has no price for a card it falls through to the next slot you configured. On the standard TCGplayer source those price points are one value per printing with no condition in them, so Low and Direct Low are the cheapest copy listed in any condition rather than the cheapest Near Mint copy. A Near Mint offer built from either can be priced off a played copy, because step 2 then applies your Near Mint modifier of 100 percent to it. TCGplayer SKU is the source that splits the price out by condition.
2. Condition. The price is adjusted for the card condition using your condition modifiers (for example NM 100 percent, LP 90 percent). If you choose TCGplayer SKU as the price source instead, each condition is priced from that condition's own market price rather than from a percentage of Near Mint. Those per condition prices can drop off sharply, so changing a card's condition can move it into a different Cash and Credit range, or out of your ranges entirely.
3. Cash and Credit Ranges. This is where your buy percentage comes from. Each range covers a band of card values (its Min Price and Max Price) and pays a set percentage or a fixed amount, with cash and credit configured separately. A card is paid based on the range its value falls into.
4. Cards outside your ranges. If a card value is below your lowest range, above your highest, or in a gap between ranges, it is only bought when the "Buy cards priced outside your ranges" toggle inside Cash & Credit Ranges is switched on. That toggle is off by default, and while it is off those cards show an offer of $0 regardless of your Fallback Cash Percentage and Fallback Credit Percentage. With it switched on they are bought at those fallback percentages, and a fallback of 0 still means not bought.
5. Hotlist, Darklist and Name Filters. A hotlist match adds a boost, a darklist match subtracts a penalty, and a name filter match subtracts its penalty.
6. Other modifiers. Rarity, printing (such as foil), and language modifiers are applied if you have set them.
7. Fixed overrides. A card listed under Buylist, Config, Product Lists, Fixed Buylist takes the cash and credit you set there, or that card’s own percentages, instead of the calculated price. The amount you enter is treated as the Near Mint price and the other conditions scale off it using your condition modifiers.
8. Rounding. If you set a rounding increment (per game, or per individual price range), the final cash and credit offers are rounded to that increment as the last step. The direction is Nearest by default, and you can switch it to Round up or Round down per game.

Bulk Price Rules sit outside this order. A card that matches one of your Bulk Price Rules takes that rule's cash and credit values instead of steps 2 and 3, gets the same flat offer for every condition you accept, and skips the rest of the calculation. Your hotlist, darklist, name filters and stock limits still apply on top. Bulk rules are matched in the order they are listed, first match wins, and a rule with no rarity, language or printing selected and no Min or Max Price covers every card in the game.

The result is shown as both a cash offer and a credit offer, and credit is usually higher than cash. All of these settings live in your Buylist Price Config and are set per game, so each game can be configured differently.