Budget what you can reasonably afford, that you can pay for outright without going into debt, and that doesn't make you "wedding poor" (i.e. you cannot do anything else because all your funds are going toward the wedding). Averages are really subjective, and depend on location, how large the guest list is, type of wedding, etc. but you will typically see "averages" somewhere in the $30K range. That doesn't mean that is right for everyone.
I think the average wedding cost is in the $30k range. It really depends on where you are, what you want and how many guests you have.
Average wedding cost in 2020 was like 19k, lower than it has been - used to be about 28k - 30k. I'm having mine at a venue and will be spending roughly 20-25k. Its doable for 10k but you'll really have to stick to a strict budget to make it happen
Budget depends largely on your location. A large city will be more expensive than a small town. Even in a large city, you can make a small budget work but you have to get very creative and nix everything labeled “wedding “ which vendors will bully you out of.
It's important to remember that you don't have to have many of the things the wedding industry wants everyone to think are necessary. A marriage license and a licensed officiant are all you really need for you and your SO to be married. If you want to invite guests then a location that provides adequate comfort for your guests and a catered meal or refreshments appropriate for the time of day are needed. Everything else is extra. There's nothing wrong with wanting extra things, but you shouldn't go broke or into debt for it.
If it’s a true backyard wedding, then I think it can be done. The biggest expense outside of a venue is the food and drink — if you trust the culinary abilities of your friends and family, make it a BYO potluck! Keep the guest list on the small side, thrift cool cups and plates and other deco. I have a friend-of-a-friend who had a backyard wedding and gave out disposable cameras instead of hiring a photographer, which resulted in some pretty cool pictures. With the right guest list and and some creative thinking, a backyard wedding for under 10k can be done. Good luck!