To be honest we have done a few and after having done a few just rebuild the thing, its not like you need to redesign get a lightweight drag and drop builder clean blank theme and go to town.
Visually Joomla designs are not complex by nature, they cant be, so its not something that should even take you more then a day or two to layout, template the stuff and then get your data across.
Whatever functionalities you have on Jooma I guarantee you you will find in the WordPress plugin repository if you cant code it yourself, I think a lot of guys think a one click migration is the quicker route, maybe in some cases, but it a technical process and needs a lot of checking.
Export what you can like products ect ect reformat for WordPress import, if you don't know WordPress well I can understand why one would want a quick solution.
Otherwise, hire a web dev to do it for you. If you value your time, the time you save debugging and fixing paths, and finding replacement plugins to fulfill functions, just like with professional
Canadian web design, will more than make up for the cost of getting a dev to do it.