The math of chasing one card
Here is an illustrative example, with made up but realistic numbers. Suppose your chase card shows up in roughly 1 in 200 packs and packs cost 4 dollars. On average you would open about 200 packs to find one copy, which is around 800 dollars of sealed product, and average means many people spend more than that before hitting. Meanwhile the single might sell for 40 dollars. The pack route costs roughly twenty times the sticker price of just buying the card.
The other packs you open along the way are not worthless, since you get bulk and smaller hits, but their combined value almost never closes a gap that size. When your goal is a specific card, the market has already done the randomness for you and priced the result. Buying the single is paying for certainty, and certainty in this hobby is dramatically underpriced.
When packs genuinely make sense
Packs are a good purchase when the thing you want is the experience of opening packs. That is a real product. The suspense, the ritual, the group chat reaction, the tiny ceremony of the foil catching light. If you enjoy that and budget for it like entertainment, packs are a perfectly reasonable thing to buy, the way movie tickets are reasonable even though you do not get to keep the movie.
Packs also make sense structurally in some games. Limited formats like draft and sealed require unopened product by definition. New players building a starting pool from nothing can do fine opening a discounted box. Collectors who want sealed product as sealed product are buying a different thing entirely. None of these are chasing one card, which is the specific trap.
When singles win, which is most of the time
If you are building a deck, singles win almost every time. A deck needs specific cards in specific counts, and packs deliver random cards in random counts. Pricing out the full decklist on a singles marketplace is nearly always cheaper than opening product until the deck falls out, which it will not.
If you are completing a set, a mix works. Open some product for the fun and the commons, then buy the stubborn rares as singles instead of opening ever more packs to fill an ever shorter list. The last few cards of a set are exactly when pack odds are most brutally against you, because you are rolling low probabilities for very specific results.
The honest hybrid strategy
Decide before you buy which product you are purchasing, fun or cards. If it is fun, buy the amount of sealed product your entertainment budget allows and let whatever you pull be a bonus. If it is cards, make a list and buy the list. The expensive mistake is buying packs while telling yourself it is an efficient way to acquire specific cards. It is not, and no blessing from us changes that, because our blessings change nothing, as noted on every page of this site.
A useful gut check before ripping product for a chase card is to look up the single's price first. If you would not pay that price for the card directly, you definitely should not pay several times that price in packs for a chance at it.