I have to say that one to two was a jump but going to three and more is huge! When I had my third, I didn't have a car that could hold two car seats and my oldest boy so I had to get an SUV. I have a three bedroom house so I had to put two in one room. My second one was still in diapers when the third was born so that cost doubled (not for long though). And the hardest part of all - my husband and I are outnumbered!!! Before he could take one I could take one, now there is one lingering if the other two are acting up or need attention. When my oldest has homework to do (in 4th grade it is a ton) I have to be able to help him and manage the two others to make sure he can concentrate. It is very difficult.
Now all that being said, there are times me and my kids all cuddle up in my bed and watch a fun show or we do a project or their little heads peak around the corner in the morning looking for me and it is undeniable, I LOVE MY LIFE! No matter what happens, no matter how hard things get these little people are the best and I am so blessed to have them.
I also want to note that my husband has long periods of time where he works day and night or has to travel for long periods. Believe it or not, sometimes it is easier, I can keep control of my schedule with the kids. My husband is not that scheduled of a person and I tend to spoil the crud out of him so our timing as a family gets a bit off when he is around at night anyways.
Last comment, I turn 40 in a few weeks and can honestly say, I would love to have a couple more kids (my husband would probably cry if he heard me say that, loves his kids but I think it is just a different thing for him, he has enough). In short, the clock has never really stopped ticking for me. I set in my brain with the last one that "this is it" "no more". I had that baby girl and the thoughts were gone. I want more! Ultimately, I have chosen not to have any more for several reasons, but it doesn't mean my clock stopped.
Just do a pros and cons list, get a real deep rooted input from your husband on it (this is real important). You will know the right thing to do.
Good luck and happy parenting.