We charge €35 for 1 hostel trip, €45 for the second hostel trip (paid activities at that one) and €100 for 2 night summer camp. Reductions for siblings.
But that is also subsidized by the subs that come (what used to be €2 per week - it’s now €20 per term) during the year. A significant sum for overnights comes from that.
Overnight costs are the hostels/campsites (expensive),activities on 2 trips (we take them on hikes on 2 but the 2nd hostel trip needs a session before we leave, camping involves a lot of activities).
Food for everyone - fruit to snack on, substantial dinner as they’re hungry after all their activity, supper (hot chocolate and Lidl versions of penguin bars) when they are homesick and we need to keep them happy going to bed, cereal, juice and bread for breakfast, bread/ham/cheese/jam for lunches along with fruit and crisps, drinks (remember the heat last summer? trying to keep Cubs hydrated in that was fun!).
First aid supplies - you go through a surprising number of plasters with penknives, and various other incidences.
Firefighters (although I’d happily take a firefighter too!! 
) and marshmallows for campfire.
Batteries for torches and kerosene for lamps. Gas for the gas rings. Usually buying an extra bag of ice for the most vital cooler as the blocks are never enough. Cleaning things and bin bags.
We have all the equipment gathered over years - marquee, tables and benches, axe and saw, gas rings, lamps. The pots and utensils for cooking, wash up bowls, serving bowls, etc. Which all have to be transported.
I use my personal coolbags as the Group cool box is not suitable for our use (Scouts go for 10 days and have a massive yoke). I use quite a lot of personal gear to make things easier and not spend Scouts money where possible.
We have tents, but the old ones were more than 20 years old so had to be replaced last year. On average, the Scouts replace 2-3 tents per year so the Cubs has done well to mind theirs so long. But a Cub tent is over €200, whole Scouts ones are larger so roughly €450 each.
I always need supplies of paper and pencils on camp for early risers or rainy days (and I do mind these to reuse as much as possible - but there’s always a few lost).
And sun cream - even though it’s on the list, there are always parents who don’t bother.
As a leader, I spend significant time, and significant amounts of my OWN money, on activities and gear for Cubs. Including getting personal gear different to what I would choose if it was just for my own use. And having spare waterproofs for those who didn’t bring theirs, or a hat for the kid who gets too cold. And a bag of sucking sweets to rally them all on cold days when things haven’t gone to plan - that never comes from Cub funds.
Leaders do not get paid. They take annual leave to bring Scouts and Guides away. They spend their own money on petrol. After getting to bed at 2am after all the hyper kids have finally settled for sleep, They wake up at 3 am because someone is homesick or physically sick and sort those out. And then again at 5.30am because it is bright and the kids are too excited to be awake and stay in bed. They may have to stay up for a parent to come and collect a kid, or even bring a kid home in the middle of the night.
They keep cheerful faces the whole time, organize the chaos 101 different ways, solve disputes about who is sleeping where, stop banter before it gets to bullying, teach the kids stuff and persuade rheum to keep going all the way to the top, celebrate their achievements, make sure to keep an eye on the quiet ones that they are ok too, .....keep everyone calm if something happens like a bee sting or slightly messy cut (nothing can panic 8-11 year olds like a little drama, and boy does it become a big drama fast even if there’s nothing to worry about).
And then they get to go home with their dirty gear and the bag of lost property. Hopefully to sleep rather than have 50 queries about lost property or “my child says....” to deal with. Or at least say hello to the rest of their own family.
Very very occasionally there might be 1 or maybe 2 parents will say Thank You (we usually bring 20-25 away).
£40 for 2 nights is very cheap.
How much would it cost you to bring your child away for a weekend, before you even add in all the skills that she will gain (including leadership, working in teams, dealing with adversity etc - not just how to pitch a tent and wash the pots) and the fun and friendships, from being in Guides.