If you don’t mind digging and you have the time to spare then a tiller may be just a waste of money because it’s not like a mower that’s used regularly. And, if you’re prepared to mostly hand dig your patch for exercise or more control, having a rotary tiller on the odd occasion for when you don’t feel like digging seems to be an unnecessary luxury purchase for the person who has it all in the shed.
On the other hand, if you do spend a great deal of time in the garden and deplore cultivation time as a necessary chore you wish could be done faster, then buying a power sweeper hoe will definitely free you up to have more time planting and fiddling in the garden instead of digging.
A tiller could have the weeds and grass dug in and soil aerated in one day. However, a large sandy area or loose soil can be dug rather quickly and if digging is easy going, then a tiller would get the job done quickly but against cost it just may not be economical and you might be better off hand digging for just that few extra hours a tiller may save.
Having a tiller is not an essential piece of machinery, like a post hole-digger for a small acreage. It’s nice to have but just the same if you don’t have the money to spend you can still do the job manually by hand with garden tools. Don’t forget you can hire moto mowers/rotary hoes for those one-off times when you just want to get a bed started and then once the soil is loose you can turn it by hand in the future.
There are lines of thinking in modern gardening circles that are leaning towards minimal soil disturbance rather than turning the heck out of it. The reasoning behind minimal soil disturbance is the belief that by over tilling the soil you upset the natural nutrient balance and also disturb or kill good bacteria and animals, which benefit the soil greatly.