Another migrant family here. We live in Europe so don't spend anywhere near that much money, but I feel your pain. For us as well as flights there's the hire car, a hotel, a couple of nights in a cottage, etc etc, all so we can travel round the country with two travel-sickness prone kids to visit family and friends. We've had a couple of years when we were struck by the lurgy, and there's nothing worse than travelling with colds etc. Aaargh!
However, I think we're lucky in that practically everyone we're going to see does make a big effort to make our visit special. In fact we have a good time planning meetups in the lead-up to Christmas. For some reason we have loads of friends in one city in particular, so usually plan a gathering, usually a winter walk with lunch somewhere kid-friendly. Not all these friends see each other regularly either, some are travelling to meet up, and that's a nice feeling too - a big Christmassy get together.
If we meet friends in smaller groups it's usually around an activity, a walks, park, art gallery, museum, NT property with a nice café, country pub, so kids have fun and you do something memorable.
As for family, we make a lot of plans in advance too, and we're not shy about suggesting things we think would be fun and politely turning things down, if it sounds like too much, "that won't be possible," but we always try to suggest alternatives that we think everyone will enjoy.
For example, there's a lot of typically British stuff that we miss, and relatives back home often find it funny to do touristy things local to them which they wouldn't otherwise do, or find us a really good curry house, café for posh afternoon tea, pub, fish and chip shop etc. all stuff we find familiar and exotic at the same time.
You also have to remember that some of the people you're visiting will not see it from your perspective at all, you have to be proactive. For example we are now really clear with grandparents and uncles and aunts about presents - they often used to buy us big bulky things without a thought for how we'd transport them round the country or get them home - and sending them by parcel would end up being more expensive, in some cases, than the gift itself. We're not ungrateful! We always appreciate the thought! (although we wish great grandma wouldn't go overboard bulk-buying cheap kids' clothes, no need!) But now we check in advance what presents people want to buy, and suggest things the kids might want that are smaller and more manageable. Less is more anyway!
So on balance, despite the hassle and expense, I feel positive about going back. Some family visits over the last few years have been stressful and emotionally draining, but I think we're getting better at anticipating that and being firm about our plans.
Be proactive, be clear with people, make sure you have planned plenty of things that you genuinely look forward to doing and that will be happy memories. Get people out of their houses to do something special, if you can. Give yourself room for downtime. And good luck to everyone who's going back home this Christmas!