Reddit mentions of CARAPEAK 25kN Screwgate Locking Pear Shaped Climbing 4 Pack Set HMS Carabiner, Aluminum Rock Climb Clip for Rappelling, Belaying Black

>over $600 to start

If you want a cheaper version of the above, without having to buy all the Slacktivity equipment (I live in the USA, so importing all that comes out as quite pricey), you can do the following:

• Buy 2 cheap stainless shackles and approximately 20-30 feet of 1 inch tubular webbing (any type will do). Tie a frost knot (or an overhand on a bite with extra slack will do, as there is essentially 0 force on this ever) in one end of the webbing, and make your own soft release.
  
• 3 - 5 of these 1 inch pulleys off of amazon. Use a grinder/hacksaw/drill to grind off the metal nub on the end, and go to the hardware store to buy some locking nuts, washers, and a 1.75" bolt.
  
• Some skate bearings off of amazon (4 bearings per homemade webbing pulley). These go over the bolts, with washers in between, of the pulleys that you took apart to make a homemade set of these. Buy some cheap pear carabiners to go with them. You have now made your own highslides/cheap hangovers for 1/3 - 1/2 the price depending on how many you wanted.
  
• Find a 3d printing service near you and 3D print your own linegrips. Buy some very thin rubber (most people recommend the 1 mm vibram sheets, but I used this cheaper one and it works fine) and super glue, thread it with ~6mm cordelette and you have your own linegrip. Do this as many times as you want.
  
• Tie some cordelette into bunny-ears knots with differing lengths on each one, and clip your homemade webbing pulleys to each loop. The loop lengths should be long enough that your webbing pulleys don't hit each other. Clip one of the sets of webbing pulleys to your home-printed linegrip, and the other set to anywhere on your anchor. These are your homemade soft RPs.
  
• You need 1 weblock. For price, instead of buying 2 stainless shackles, just get 1 and buy the cat-on-slack soft release to hook in directly to your soft release. Or get the normal weblock they sell and hook it onto your stainless shackle. For weight, get a weblock that does not have sharp edges at the connection point and use a soft shackle (discussed below) to connect it to your soft release (like the alpine weblock or use a purelock to go straight into your soft release, both of which are pricey).
  
• Don't buy pre-constructed soft shackles, as they gouge you for the price. Buy your own 1/4" amsteel and make your own soft shackles (1 or 2 is fine for long-lining, make 4 or 5 for highlining as you will swap these out for the steel ones on your soft release).
  
• For anchors themselves, buy static rope. There are plenty of options out there, and what thickness/weight/breaking strength you want depends on your personal priorities in anchor construction, so I won't make a specific recommendation to you. Canyoneering static rope tends to be better in terms of weight/breaking strength, but is pricier. Depends on what you want.
  
  This allows you to use the above posted method, even up to a 27:1 mechanical advantage (if you 3d printed 3 linegrips, with 5 pulleys so you could put 2 extra 3:1 multipliers on a 3:1 system) without losing efficiency. Rigging 100m in the park is impossible just using normal carabiners; you really need the webbing pulleys/hangovers. Best of all, you've accomplished this at a fraction of the price of buying pre-made gear, and none of your janky homemade pulleys or linegrips are life-dependent pieces of gear if you went highlining.