my DS went from cubs toscouts at 10 years 9 months - I think you go up between 10 and 11 depending on space in teh group.
so far in scouts he has got a swimming badge, first aid badge and a creative badge, gone ice skating, various night hikes, had a film and takeaway evening, taken part in a 'scouts have talent' night, been away on an adventure weekend, there is a 'freezer camp' booked for the last weekend of half term.
His group is pretty active, they have a good mix of boys and girls, and although he is the youngest he really enjoys it.
DD is in the cubs, and has taken part in a similar range of activities and camps.
I think how good it is can vary depending on gthe group and the leaders - we are fortunate in that ours are energetic and committed and put a lot of effort in.
regarding cost, we pay by direct debit, think it is about £10 a month per child, but with a discount for 2 or more. That covers the majority of stuff, but we were asked to pay more for swimming and ice skating.
camps vary in cost - the adventure one was £70 ish for the weekend, quite expensive but was excellent, they took part in lots of activities at a PGL centre, so was much cheaper than if we had done it independently. Ordinary weekend camps cost £35 ish, and are, according to my kids great fun.
YOu also have the uniform to buy - £12 ish for a sweatshirt for cubs, or similar for a shirt for scouts, plus neckerchief. YOu can sometimes get second hand uniform, and you don't need it for the first few weeks
hth