Can a 15 year old girl make her own XC jumps?

My family is moving to a bigger propery, and I'm really exited about having my own paddock full of xc jumps!
I just looked at a website where my pony club got some new jumps from, and I was shocked to see that a simple 60cm rolltop is about $400! I honestly had no idea they would cost that much.
Is it that hard to make my own? I can get some help from my dad who can make absolutely everything, but he's a self-employed electrician and doesn't have that much spare time.
What are the approximate costs of materials and such (I live in Australia) and how long would it take to make them?
Thankyou in advance :)

Definately do-able, you just have to be willing to work hard and be creative! You may not get the variety, but you can never go wrong with simple log stack jumps. It basically just entails stacking small pieces of wood to the height you want! Tires are also excellent - you can get bigger ones and half bury them in the ground so just the upper crescent is showing, or you can sink two posts and nail a rail to them with tires strung tightly along it. You can often find places to get cheap or even free tires that are older and unuseable.

Also stay on the looking for larger trees that are ready to come down, or have already fallen. Just 2-3 of them stacked on top of each other with a post sunk on both sides at both ends will hold them!

And if you're feeling REALLY ambitious, you can even dig yourself a ditch for a water complex!