A cheaper way is to get yourself a spare battery from Costco (bosch or the like) and some leads.
I have to say that this whole thread confuses me a little. I've jump started loads of cars in my time, never had a problem and would be very surprised if I had to. All you are effectively doing are increasing the cell composition of the battery and therefore theortical ampage of the battery (ie: bigger battery!) when you provide a boost / jump. The damage you are talking about would occur to either cars alternator due to:
1. The boosting car - battery has increased load - possible alternator damage
2. Flat car - alternator piling current into flat battery = working hard.
In the either case surely the same applies when the alternator is under hard load ie:cold winer morning - deminser, heated seats, lights and radio playing from cold start?? Therefore assuming you don't try am jump something out of your league (so as to speak) then you should be okay.
I think you would have to be very very unlucky to fry anything either car (assuming they were or relative cranking amp ratings). As for the voltage jump - I would think the battery would absorb the majority of that as "charge" - you need more than 12v to charge and 12v battery. Also, if the voltage spike was so bad, the fuses would go pop (unlikely).
I caveat this as I am not an electical engineer and so may be talking absolute rubbish....