last week some dutch tech site build a 'cheap' litecoin/dogecoin mining machine

1  AMD Athlon II X2 340 Boxed    € 33,71    € 33,71
1  Asus F2A55-M LE    € 46,37    € 46,37
2x Club3D Radeon HD 7870 '13Series    € 141,50    € 283,-
1  Rasurbo BC-10    € 23,56    € 23,56
1  Transcend JetRam JM1333KLU-2G    € 19,38    € 19,38
1  be quiet! System Power 7 450W € 51,-    € 51,-
Total € 457,02

But ofcourse you can buy 2x more expensive graphic cards etc.
Hope it helps a bit, also tweaking underclocking/overclocking parts the system a bit, can improve the speed, and the watt used.

Merry christmas people,
the wind and rain has stopped here, sun shining.

Wish you all some nice days, have a good time with friends and family.

Keep the spirit up, and the warmth glow of those mining machines
peace