We shut the car off and restarted it 5 times in a row and each time the GB40 started the EJ257 like nothing. We could have gone on longer, but we didn't want to foul the cars plugs with continuous dead cold starts with no warming in between. EJ plugs are a bitch to change! Afterward, the indicators said we had over 75% of the batteries charge remaining, so we believe that it can do 20 starts.
A $124.95 list price is suggested on NOCO's website but shopping around online the GB40 can be found for under $90. That's $90 worth of security well spent. Even if you don't use it as a jumper, it is a great super backup battery for your mobile electronics!
We are gonna get a few for our personal cars and charging things during grueling trade shows and races!