I am building 2 picnic tables for an eagle scout project and was wondering what the cheapest good wood is?

Redwood is too expensive… I need something cheaper.

It is an outdoor picnic table.

I was wondering if treated lumber is really that bad? because if i paint or stain it, i will be covering up the "poisonous" stuff… it is also by far the cheapest i think.
If you know the average price of the wood you recommend, could you please tell me that.