I have no idea how much all the work travel I have done through more than 20 years has cost. I am sure it is in the hundreds of thousands of dollars. I have visited at least 28 of the states (USA) for work, and had students with many for many of those.
I have been to scientific meetings in or worked in Canada, China, Columbia, Japan, and Mexico. Sometimes I was gone for weeks at a time, staying in hotels, and there were so many plane tickets I cannot even begin to remember them all.
But, in almost all cases my employer, whether university, industry, or nonprofit has covered almost all the expenses associated with my travel. In some cases, I had to pay the balance between what the state/university allowed as a per diem for lodging and meals, and what the actual cost was, but usually I was able to find lodging within the budget, even if sometimes I had to have a roommate.
When I worked for industry, they would not pay my expenses to some scientific meetings, so I had to fund those myself.
The university or grant money covered all expenses related to doing research. The consulting firm covered all expenses for equipment and its use and travel necessary.