There is no major difference in the price of A3/A4
Using an A3 printer scanner in home based office set up can be really advantageous, especially if your daily schedule involves lot of printing of memos, advertisement, and other documents that are larger than the standard A4 size sheet.
Basically, if you buy a smaller size A4 printer, you don’t end up saving a substantial sum of money. You will see that you are spending a large amount of money in getting A3 size documents printed from outside.
There is no major difference in the price of A3 and A4 size printer (unless you are buying a branded printer scanner which is very popular and expensive).