Allright, I have tons of disposable income. I'm planning to get Binding of Isaac: Afterbirth. Can y'all recommend other games in about that price range or lower?
Going alphabetically through my Steam library for you. Prices in USD. Heeeere we go:
Beat Hazard ($10) is an oldie but a goodie. It's a simple space shooter like the old Asteroids arcade game, with as many levels as you have songs on your computer. The speed of a level is based on the tempo of the song you choose, and the level is as long as the song. If you want to torture yourself, play using Nightwish's "Fantasmic" or anything by Nightcore or Dragonforce.
Breath of DeathVII/Cthulhu Saves The World ($3 for both) are 2 hilarious retro RPGs. Lots of Lovecraft and gaming parody, typical NES-era gameplay.
Castle Crashers ($15) has been infamous since it came out on the XBox 360 back in '08. Pretty sure it's well-known in Finland, but just in case it isn't--This game is by the founders of Newgrounds. It has the sort of humor you'd expect from the people of Newgrounds. Single-player is pretty hard, but I wouldn't mind doing multiplayer if our schedules sync up.
The Cat Lady ($10) is psychological point-and-click horror. You play as a suicidal 40-year-old woman who's lost her grip on reality. Good if you like TONS of gore.
Child of Light ($15) is a sidescrolling RPG with gorgeous graphics and an unusual combat system that I happen to like. I adore everything about this game; however, if rhyming dialog for EVERY SINGLE LINE bothers you, you may want to skip this one.
Defender's Quest: Valley of the Forgotten ($15) is a tower-defense game with old-school 16-bit levels and a really good story. You play as a librarian who suddenly finds herself with magic powers, a mad barbarian, a rebellious archer, and other cool characters (including a fucking DRAGON that you meet at about the halfway point). Multiple difficulty levels, lots of fun achievements, and really great dialog between characters. If you like tower-defense, you pretty much NEED this game.
Ms. Splosion Man ($10) is just plain zany platforming fun. If you like 2D platformers AT ALL, buy this game. It's awesome and has a decent amount of challenge to it.
Never Alone (Kisima Ingitchuna) ($15) is gorgeous and based on traditional Inuit folklore. You play as a young girl and her fox friend, trapped in an endless blizzard. Another 2D platformer, but this one is a fair bit easier with a game controller. Worth it to play even with a keyboard, though. (The default graphics can be a bit resource-heavy, though, especially on old computers.)
Portal and Portal 2 ($10 and $20 respectively; $25 for the bundle) are stupidly popular for a reason. If you still don't have them, why don't you have them? Remedy your lack of Portal games immediately.
Skyborn ($15) is a retro-style JRPG set in a steampunk universe in which humans are ruled by the winged Skyborn. It sticks to the usual formula of JRPGs, but that's not really a
bad thing. Plus, the cutscene graphics are UTTERLY GORGEOUS.
The Stanley Parable ($15) basically subverts every single expectation you have of video games. To quote the game description: "The Stanley Parable is a first person exploration game. You will play as Stanley, and you will not play as Stanley. You will follow a story, you will not follow a story. You will have a choice, you will have no choice. The game will end, the game will never end."
Waveform ($2) follows a very simple concept, but is a really good challenge with a well-thought-out learning curve. Travel through the solar system from Pluto to the Sun, as a wave of light. Avoid the black obstacles and don't get swallowed by the Singularity. You can change amplitude, period, and color of your wave. Worth well more than its actual price tag.
The Yawhg ($10) is short, simple, and quite fun. It's a good game for when you have friends over (1-4 players alternating), and each person's actions affect what you encounter in the weeks before and after the Yawhg's attack. (No, you don't actually get to fight the Yawhg.) Among other things, I've become an arena champ, a werewolf, and a respected healer. Events that occur at each place are randomly generated from a large pool, so it's never the same game twice.