Your Steam level is driven by one thing: crafted badges. Each badge you craft grants profile XP, and enough XP moves you up a level. Almost nothing else on Steam contributes.
Crafting a badge requires a complete set of trading cards from a single game. That is where the difficulty comes in — playing a game drops you roughly half its set and then stops. The cap is deliberate, and it is why a market for individual cards exists at all: the second half of every set has to come from another player.
None of it affects gameplay in any title. Steam level is a profile feature, and the honest reason most people raise it is that they want the profile to look like they have been around.
A booster pack contains three random cards from one game's set. If you are completing a badge, random is exactly what you do not want — you will pull duplicates of cards you already hold, and each duplicate is wasted money toward that badge.
Buying the specific cards you are missing avoids that entirely. It is why the calculator above works from set prices rather than booster prices: for a target level, the cheapest route is almost always to buy the exact remainder of a set outright.
Levelling also gets progressively more expensive. Each level requires more XP than the one before, so the badges that took you from level 5 to 10 will not take you from 100 to 105. The calculator prices the real curve instead of quoting a flat per-level figure.
Signed out, set your current and target levels and it estimates what closing that gap costs at current market prices. Nothing is required — no account, no sign-in.
Signed in through Steam, it reads your actual level and inventory, so the plan becomes specific: which sets to complete, which cards you already hold, and what the remainder costs. From there the sets can be bought directly, and everything listed is in stock and held by our trading bots, so there is no waiting on a seller.
If you would rather browse the cards yourself, the Steam trading card market lists them individually, and the seller fee there is 20%. Mannco.store also runs full marketplaces for CS2, TF2, Rust and Dota 2, with a shared balance across all of them.
Profile showcase slots, extra friend-list capacity, a larger share of the booster-pack drop pool, and a badge on your profile. Nothing about it affects any game you play — it is a profile feature, not an account privilege.
Because playing only ever drops about half of any card set. Valve caps it deliberately, so the remaining cards have to be traded or bought from other players. That cap is the entire reason a card market exists.
Usually, yes. A booster pack is a random three cards from one game's set, so completing a badge through boosters means buying duplicates you already have. Buying the exact cards you are missing costs less per badge, which is what the calculator above prices.
No. Signed out, it estimates the cost of going from any starting level to any target. Signing in through Steam replaces the estimate with your real current level and an account-aware plan you can buy directly.
No, and it gets more expensive as you climb. Each level needs more XP than the last, so the same number of badges takes you further at level 10 than at level 100. The calculator accounts for this rather than quoting a flat per-level price.