(thanks vijf - took the sales from the other suggestion and put a few new ones)

https://marketplace.tf/items/tf2/727;6 - (non prof.)

Nov 18: 549$, keys 1.78 each so 549/1.78 = 308 keys

bought today - https://imgur.com/a/l6Agirq = 315 keys

- considering that the price of the prof. ks. is pretty cheap, we can basically ignore it

https://marketplace.tf/items/tf2/727;6;kt-3 (prof.)

Jan 1: 629.99 at 1.78 per key = 353 keys (new)

Dec 4: 555.56 at 1.76 per key = 316 keys

Dec 4: 579.99 at 1.76 per key = 328 keys

Dec 1: 579.99 at 1.78 per key = 326 key

Nov 20: 599.99 at 1.78 per key = 337 keys

- older sales seem to hover around that $600~ price

* edit (adding sales from mannco): *

https://mannco.store/item/440-professional-killstreak-black-rose

Dec 9: 600 at 1.64 per key = 365 keys

Nov 23: 549.99 at 1.65 per key = 333 keys

- older sales seem to hover around that $550~ price

https://steamcommunity.com/market/listings/440/Professional%20Killstreak%20Black%20Rose

Nov 25: 864.90 / 751 after tax

Nov 20: 462.80 / 401 after tax

Oct 29: 821.02 / 713 after tax

- if we do a mean price, we get about $621, which comes close to mp.tf (considering that SCM is usually overpriced)

overall, the current price suggestion is pretty low and doesn't really reflect the market (https://imgur.com/a/ShQPB9X - buy orders exceeding the suggestion price), the marketplace sales and it's current listings do suggest that the price usually hovers around ~340 keys, but considering that one sale was made today for 315, a range of 315-360 is viable

- hopefully the suggestion is good, it is my first (actual) suggestion! have a nice day :)