I know of one accountancy firm (I can't name due to confidentiality) will do the payroll processing for 8 euro per payslip. This rate applies to a company with approx 30 employees, half of whom get paid weekly.
I have no idea what the rate would be for 2-4 people, but it might be worth getting some quotes from accountancy or payroll/HR firms. There are lots of these firms.
Also, try and think beyond the mere transaction. There can be lots of queries that can be a distraction, such as: pensions, tax, allowances, HR advice, etc.