Is it permissible for a traveler to combine and shorten prayers if he chose a slower and cheaper means of transportation, even though he could afford a faster one, in order to save money?

There is no objection to a Muslim choosing a means of transportation for his journey, whether it is slow and inexpensive or fast and costly. This does not affect his right to avail himself of the travel concessions, for what is considered in travel is only the distance, not the length or shortness of time.