Hats based around the average price of the Greased Lightning include: Baseball Bill's Sport Shine, The Fed-Fightin' Fedora, as well as the Death Racer's Helmet.

The Death Racer's Helmet is currently being sold at 60 keys Pure:

http://backpack.tf/classifieds?item=Death%20Racer%27s%20Helmet&quality=5&tradable=1&craftable=1&australium=-1&particle=107&killstreak_tier=0

Baseball Bill's Sport Shine is not currently listed on the market, however, is priced at 84 Keys:

http://backpack.tf/stats/Unusual/Baseball%20Bill's%20Sports%20Shine/Tradable/Craftable/107

Although the Sport Shine is regarded as a slightly more expensive hat, I took that into consideration due to

other effects of the Greased Lightning, such as the Starstorm Insomnia, are being currently sold at 60 Keys:

http://backpack.tf/classifieds?item=Greased%20Lightning&quality=5&tradable=1&craftable=1&australium=-1&particle=109&killstreak_tier=0

The effects were added in the same update, however differ in average price by approximately 12 keys.

The Fed-Fightin' Fedora is also regarded as slightly more expensive hat, with the average price being ~70 keys and the Greased Lightning being only ~68. The Fedora's Neutron Star variant is priced at 31-37 Keys (~34 Keys), however the price being out of date by 4 months.

http://backpack.tf/stats/Unusual/Fed-Fightin'%20Fedora/Tradable/Craftable/107

Sellers of the Startstorm Insomnia varient however are currently selling at 65 Keys:

http://backpack.tf/classifieds?item=Fed-Fightin%27%20Fedora&quality=5&tradable=1&craftable=1&australium=-1&particle=109&killstreak_tier=0

In Conclusion, 33-38 Keys for this hat would be a fair price for this hat