Well, not all the blue materials have the same prize, the useful ones you can sell really cheap, which ones are those useful, check your inventory and you can realize that from the common ones you have plenty of them and the useful ones probably 1-2 or none at all.
For example, the battery is difficult to get and you can sell for nothing but the others purple parts you can sell for more than 1k because are easy to win.
Gray parts useful: fuse and mounts was difficult to get at the beginning when upgrade my Subaru BRZ, now have plenty of them.
Green parts useful: relay and gasket.
Blue parts useful: bearing, hose and bead wire.
Purple parts useful: battery, battery and f$-&: difficult to get battery.
Yellow parts can sell for the same amount because all of them are easy to get in Turner Trials (if you have the Viper).
Happy racing!!