Depends on what brand of Adult diapers you buy but a case of Adult diapers usually costs around $70.00 and you might need 2 cases of Adult disposable diapers for your incontinence for 24/7 diaper wearing.
You may or may not go through both cases but you'll be spending at least $140.00 per month on 2 cases of adult disposable diapers.
$140.00 per month x 12 months in a year would cost $1,680.00 per year for 24/7 diaper wearing.