Make it Easier to get to Luton Airport
The only way is to drive to Cambridge, taking into account the need to change at Bedford I reckon the rail journey will take about an hour if we are lucky, so that means leaving home around 3:30 am to park the car and get to the station, parking for a week will cost us over £60.
Assuming the fare will be similar to that to Stansted airport, four anytime returns will cost us over £99. Ah but, the first train doesn't get us to the airport station until 5:15am. That's a bit risky considering how often trains are cancelled, strikes and so on. Using trains one always needs a contingency, just in case.
All in all, reconsidering, I would not use EWR to travel to Luton Airport, I can drive there and park with all the convenience in the world in about 45 minutes. The costs being less or comparable to using EWR and I'll noyt have to hang around cold stations with my luggage, praying that the train is going to turn up and run on time.