Simple and cheap boost converter [Need help]

[senso]

Goodnight, I'm in the means of designing and creating a very cheap robot that will be used in a series of presentations that me and some friends of mine will make, so the cheaper the robot the best!
I'm facing a problem with the power supply, it will be made of 4 AA batteries so the voltage can swing from 6v to 4v, assuming non rechargeable batteries are used, and I would like to boost that voltage to 7V, because the H bridge drops about 1v and the motors are rated to 6v maximum, so that and the PWM will protect the motors as they will never or very rarely be driven full speed, and then the most probable thing to happen is that the voltage will sag/drop.
I have re-discovered Dave video about the MC34063 IC, and it seemed perfect, but the motors need 2A, well in fact its 1A stall current for each one, but I prefer to stay on the safe side and design the boost regulator to be able to put out the 2A, as there are also current spikes when starting the motors and so on.

So, if anyone could help me, is if the MC34063 with an external "pass" transistor is a good choice or should I choose another boost converter? The greatest problem is that not all the most typical ones accept voltages as low as 4v, and those that accept them are way to expensive, like the MC is 44 cents in Mouser, a single LM2677 is more than 3€.
Any ideas, tips, links to read, I'm open to it, and thanks in advance to any help provided

[mikeselectricstuff]

MC34063 is very cheap but pretty rubbish as DC/DC's go. There are plenty to choose from, and unit cost is not going to be a big part of the cost if you're only building a few, so something that's a good fit will probably save you more in time and ancillary parts cost than the difference in unit cost.