A used Wii depending on the accessories should be well less than $100, a refurbed Wii U from Nintendo about $240 with tax. If you look hard enough you can find used Wii U games for 30% off or more depending on the age of the game.
Whaaaat where? I've only found Wii plus accessories for $100, maybe its cuz I'm in Canada
If money is tight and you don't have a console get a Wii, if you can afford the Wii U get it and the. You can buy the important HD games you want at a price point you are comfortable with. If you know you will not be able to purchase any Wii U games or receive them as gifts don't buy it. There is no guarantee there will ever be backup loading.
The question you need to answer is "What games do I want to play and can I afford to play them?"
If you have a good PC and only want Wii games investigate Dolphin.
My 9 & 12 year old boys primarily want Nintendo exclusives out of a console so the other systems are not even a consideration, in a few years that may or may not change.