Will try to be brief but avoid any dripfeeding.
Christmas this year was at my parents' house. Them, me, DH and our DC (8 and 9), DB, SIL and their DC (10 and 6). We stayed 4 nights and the others are one more night then home tomorrow. We alternate between being with my parents and PIL as do DB and SIL so usually one year we are all 10 together and next year not at all. We have hosted in previous years, DB and SIL haven't as don't have room but would like to.
When we host it costs around £400 on food and booze for the few days people are with us. DB and SIL bring plenty of booze and at least one extra dessert. DPs bring a bottle and some homemade mince pies etc but also always pay for any lunches out on day trips etc.
This year although DPs were hosting DH and SIL decided to offer to cook and sort all food. We set up an order to a local Tesco and it came to £270. DP separately provided the turkey, loads of sausages and bacon and a good supply of cheese.
I had assumed we would basically split it three ways and I would ask my parents for about £90 and DB for the same. But maybe less from DPs as they provided turkey etc and spent £80 on lunch for 9 of us on 24th. DH had assumed that as we pay for all of it when we host they would do the same and give us more like £200 (shop minus all the extra booze that they will have had little of) and DB wouldn't pay anything.
I don't think either of us are right are wrong, just looking at differently. But we have nearly 2 hours of our drive left and as I've done my 2 hour stint behind the wheel I'm filling in the time asking for opinions on this!