This app can help you monitor CSGO skin weapons current market prices and also the buyers requested prices (price updates every 5 seconds!). To make it more convenient, you can also set price alerts (e.g. alert you when sell price is lower than some amount). And the item with satisfied alerts will change to GREEN in background. There is also a Link to Steam Market so that you can go in the settle a transaction.
Note: all the designs of the skin weapons come from Steam and all the price quotes data come from Steam as well. This app is not affiliated with Steam or Valve in any ways.