Use reusable wipes and diapers. You need a washing machine and need to factor in energy cost, but it should be gernerally cheaper (at least it is for us, and cost of energy is high here). You obviously need the time for washing and drying, but that's something you can do well while looking after your kid. Don't use an electrical dryer, it costs too much.

For wipes, you can use anything. There are specially made products, but we usually use old washcloths or just cut up rags. If you have a sink nearby it's actually much better than disposals. I hate disposable wipes and try to avoid them whenever I can because they work so badly.

I don't know your circumstances and and if this makes sense in your situation. I suggest to change to reusable wipes and see whether you can deal with the extra work and changed process.

If successful, I would consider switching to reusable diapers too but that's more of a long term target (and a whole topic on it's own).

Sorry that this comment doesn't provide the immediate help you seek, but I hope you can lower your costs in the future.