I have to say I'm very glad that the parents of DS's friends don't have the same attitude as you.
I recently held DS2's party - a small affair with just 8 of his new school friends invited, then there were my other 2 DS's, my BF's older DD and another friend's DS. It was at home, on a shoe string, there were no fancy party bags (they contained a piece of cake and that was it), no fancy prizes for games, and was held at home.
One of those friend's of DS2 invited him to her birthday party - a much more lavish affair held at the most expensive of the soft play centres in our town, fancy "gift bags" to take home, face painting etc etc, the birthday girl's mother even arranged (with me mentioning anything) for her MIL to pick DS2 up and take him to the party as it was going to be almost impossible for me to get him there
The reason for that was because her DD wanted my DS at her party to celebrate her birthday. Her mother didn't care that the party her daughter was invited to (DS2's) was a simple party at home, with no fancy entertainment etc on a shoe string budget, almost certainly costing no more than 1/4 of what her DD's party did.
And you know what - I@m bloddy grateful for that, as if the parents of my DS's friends based their decision on who to invite to their own DC's birthday parties on how wonderful/expensive/lavish those children's parties had been they would have been to virtually no parties at all.
YOU decide what to spend on a birthday party/'what to do for it based on your budget
THEY decide what to do for a birthday party based on the same things. And if sharing a party with 2 other people means that their DC will have really lovely party which they (and the other parents) couldn't usually afford who give a flying fuck?