Here is my cost comparison for 60" versus 70". I will stick to EF stuff. Most of this type stuff I get from tower and use their coupons which average 15% off, so prices reflect that. RX and misc cost like spinners and props are close, although the 70" is more.
60" EXP combo $430
4x 7245 $216
$646+RX, shipping ,batts, and misc.
70" EXP $389
4x 5685 $145
Motrolfly 4325-380 $170
Talon 90 ESC $66
$770 +RX, shipping, batts, and misc.
15cc project
60" EXP $260
15GX $250
Hyde mount $70
Jtec muffler $88
fuel tank $20
IBEC $40
4x 7245 $216
1x 5087 $34 (throttle)
$978 +RX, shipping, batts and misc!
This is not even including the materials I will need to use to modify the airframe. The electrics also need battery cost so this will come more in line, but that is dependent on your current LiPo stockpile. There are so many good choices in standard size servos and not many in Minis, which to me drives up this cost on the 60" airframes. For $20 more on the 70" airframe you can have the outstanding Hacker A60-6XS. To some the car size transport in the 60" class makes it perfect. When I go RCing I take my F150 which is perfect for the 30cc size.
Looking at my horrible schedule till Jersey I doubt I will get the 15cc project done, but you never know. One good "bad" weather day or two and I might blaze through it. The 110 Yak is priority #1 for a while and my motor is not even on the it's way back from DA yet. I will do up the full build thread when I get to it.