This is quite interesting as our relationship is currently the other way round a bit.
Chez 'Pru, DP and I have always had a similar income. Gifts historically tend to be bought out of spends - money left in our personal bank accounts after all of the joint expenditure has been covered. So while I agree with other posters that in a partnership the income and expenditure should be considered joint, when it comes to gifts, that's slightly different.
Last year, when DP (I think its relevant to add we are not married but live very much as a married couple and been together dince the dawn of time) was made redundant and shit hit fan financially, our joint household income nosedived. We just told EVERYONE politely and frankly that we weren't able to afford to buy gifts that year and we specifically requested none in return. It wasn't remotely embarrassing. I think for most people it was a blessed relief when everyone was finding things tight. We didn't buy each other anything either, although I could probably afforded to buy DP gifts out of my spends, it just didn't feel right somehow. It was better to just place a blanket ban on all gifts.
This year, his income is still shaky being in the middle of setting up the business and he still has no spends of his own. We're managing alright though on my (fortunately significantly increased) income so I've pretty much bought as usual for our immediate family. Extended family (ILs) and friends are just expecting things to be the same as last year - i.e. no gifts. I think the precedent is set now and I'm happy for it to remain so.
This year, I've bought DP things I know he would like but would never buy for himself, and dropped hints about something I would quite life for myself that I know is reasonably priced, as I know he would still like to stretch to buy me something.
I think you should have followed the 'Pru example and told the in-laws that its a no-gift Christmas this year. I don't see how hard it would have been in November to have that conversation, its not presumptuous if they routinely buy you gifts every year. Its too late now so you just have to be gracious and accept their gifts. Your DH will be buying gifts for them surely, so there won't be any embarrassment that you have nothing in return for them?
I must add, that borne out of the no gift policy with DPs sisters has been the establishment of a lovely tradition of exchanging small home made goodies. I think you're worrying too much about what people think.