For sure you can go way off the deep end with these engines. Especialy if you pay to have it all done.
But I got the weedie for $25 at a yard sale, CH ignition is $120, the carb $35 and the rings are $15. Everything else is modified stock. So I got about $200 and a few hours of labor in it. The only maintaince in the last 2 years has been clean the carb. Replacement parts are dirt cheap, just buy another weedie.
The basic idea is to do it your self and have fun.