Despite currently being "in-date", the low end for the previous suggestion is drastically out of date. Using 675 from the old suggestion. Credits to Torb for all the help.

Old suggestion (675): https://backpack.tf/suggestion/5c81b484d3817253f2289b06

New Sales

Sale 1:

https://backpack.tf/profiles/76561198050509345#!/compare/1556755200/1556841600

Burning pencil pusher (500) + misty ten gallon (175) + searing luchadore (39) + arcana heavy duty rag (150)* + 75 keys sweets

Capped by 850 b/o: https://imgur.com/gallery/uGpsTen

*mini for arcana heavy duty rag

https://backpack.tf/profiles/76561198021055079#!/compare/1556064000/1556150400

Sold for: purple energy tyrannus (41) + burning batters helm (86) + 40 keys

Capped by 150 key b/o: https://imgur.com/gallery/G31vpYV

Sale 2

https://backpack.tf/profiles/76561198071230830#!/compare/1553904000/1553990400

Vivid plasma viewfinder (440)* + bonzo front runner (159) + haunted ghosts wreath (155)** + 105 keys in low tiers/sweets

Capped by 800 key b/o: https://imgur.com/gallery/FguGcIO

*Mini for vivid plasma viewfinder

https://backpack.tf/suggestion/5c9b9dbed3817227d176fbe2

**mini for haunted ghosts wreath

No recent usable sales that aren't bulk or a year out of date. Going with most recent price of 155 keys.

Sale 3: (Huge credits to Torb for this sale)

https://backpack.tf/profiles/76561198056793885#!/compare/1555804800/1555891200

Sold for: 175 keys + power surge bonk boy (215) + haunted phantasm lucky shot (80) + eldritch flame duck billed hatypus (165)* + MW strange cool blitzkrieg medi-gun (65)** + WW strange isotope low profile SMG (30.5)*** + isotope wrench (34)****

Capped by b/o at 750 keys: https://imgur.com/gallery/8U2ojef

*mini for eldritch hatypus

https://backpack.tf/suggestion/5cbde95267807219145f9d6a

Taking 165

**mini for blitzkrieg medi-gun

https://backpack.tf/profiles/76561198071230830#!/compare/1556150400/1556236800 - 65 purehttps://backpack.tf/profiles/76561198093707809#!/compare/1554249600/1554336000https://backpack.tf/profiles/76561198091863983#!/compare/1554163200/1554336000 - Unu shotgun https://backpack.tf/profiles/76561198091863983#!/compare/1554163200/1554336000https://backpack.tf/profiles/76561198057452720#!/compare/1554249600/1554336000 - Another unu shotgun

Taking 65 keys

****Mini for low profile SMG

https://backpack.tf/profiles/76561198039731024#!/compare/1554768000/1554854400https://backpack.tf/profiles/76561198057452720#!/compare/1554768000/1554854400 - bulk https://backpack.tf/profiles/76561198057452720#!/compare/1555459200/1555545600https://backpack.tf/profiles/76561198056793885#!/compare/1555459200/1555545600 - bulk https://backpack.tf/profiles/76561198056793885#!/compare/1555804800/1555891200https://backpack.tf/profiles/76561198071230830#!/compare/1555804800/1555891200 - bulk https://backpack.tf/profiles/76561198071230830#!/compare/1555804800/1555891200https://backpack.tf/profiles/76561198030343929#!/compare/1555804800/1555891200 - 25 keys and a bit of refhttps://backpack.tf/profiles/76561198030343929#!/compare/1556236800/1556323200https://backpack.tf/profiles/76561198163755834#!/compare/1556150400/1556323200 - 36 pure

Taking 25-36 keys

[i]****Mini for isotope wrench[\i]

https://backpack.tf/profiles/76561198091863983#!/compare/1553472000/1553558400https://backpack.tf/profiles/76561198039731024#!/compare/1553472000/1553558400 - bulk https://backpack.tf/profiles/76561198039731024#!/compare/1554768000/1554854400https://backpack.tf/profiles/76561198057452720#!/compare/1554768000/1554854400 - bulk https://backpack.tf/profiles/76561198057452720#!/compare/1555459200/1555545600https://backpack.tf/profiles/76561198056793885#!/compare/1555459200/1555545600 - bulk https://backpack.tf/profiles/76561198056793885#!/compare/1555804800/1555891200https://backpack.tf/profiles/76561198071230830#!/compare/1555804800/1555891200 - bulk https://backpack.tf/profiles/76561198071230830#!/compare/1555977600/1556064000https://backpack.tf/profiles/76561198265550041#!/compare/1555632000/1556064000 - Mem leak drill + strange pda (20 + 14) https://backpack.tf/profiles/76561198265550041#!/compare/1556150400/1556668800https://backpack.tf/profiles/76561197964171516#!/compare/1556582400/1556668800 - Twat whirly

Taking 34 keys

Sales at: 850, 800, 750. This proves 525 is well and truly low, but since 675 is still in-date it should be included in the range. Any help/constructive criticism is always welcome.