@colorant’s answer refers to an offer by BlaBlaCar of “24€ pro Person 4 freie Plätze” for Amsterdam to Hanover.
Rome2Rio by car from Amsterdam to Hanover estimates 60€-85€ (and admittedly 19€ for Rideshare).
With four spaces available the upper end of the range seems would be more appropriate (ie 85€). Split between driver and four others this equates to 17€ per person.
The German version of BlaBlaCar’s terms and conditions does not appear to detail booking fees but the English version states the maximum is 20% of the Cost Contribution. So for a contribution of 24€ the maximum booking fee is 4.80€ per passenger. This leaves at least 19.20€ per passenger to be passed on to the driver. The ‘contribution’ from four ride sharing passengers at that rate would be 76.80€, a little under Rome2Rio's high-end estimate of total
* cost. However, five passengers (ie including the driver) at that rate would total 96€ - 13% more than Rome2Rio’s high-end estimate of the actual cost.
BlaBlaCar states “No profits are made which is why BlaBlaCar drivers' insurance policies are not affected.”
However, if Rome2Rio’s figures are to be believed, it seems drivers may be making profits and consequently the journey may not be covered by insurance (my concern).
On the other hand, 24€ appears to be a genuine and recent quote, indicating that Rome2Rio’s Rideshare estimate may be inaccurate by 26%.
Is it a mixture – Booking fees are more than 20% for this journey and/or Rome2Rio is not fully up-to-date for prices and/or 24€ is an exceptionally high example for the journey in question (perhaps because other rideshare services are more expensive, or a vehicle with very high fuel consumption)?
* It seems I misunderstood Rome2Rio's figures for the cost of driving. These, as has been explained by @Relaxed, are basically fuel-only, or thereabouts. Other 'variable' costs (ie those that also increase more-or-less in proportion to mileage) would be about the same again (tyres, clutch and brake pads, oil, filters, windscreen wipers, bulbs etc) and, depending upon usage, 'fixed' costs (eg insurance, annual certification etc) could be the same again, again.