Yes, no budget air fly this rte.=(
Yes, MH and SQ have been selling their tickets expensively, almost no chance of them offering discount. But no, not a monopoly situation... Japan Air and Garuda Indo flies the same route too, but not freq, like once a day or two... Web link to reputable TA provided...=)
Yes, taking a coach is a good option. Take only the best 16seaters at only S$40/pax/one way duration 4.5 - 5hrs, and brings you right into town. Don't underestimate this coach... visit www.transtar.com.sg
No, IMHO won't suggest you taking the senai-kl budget route... too much trouble...travelling to JB and flights subjected delay...
Taking a flight may not always be faster than coach. Remember time used early check-in, clearing customs, transfer fm KLIA (and more $$$)... too much hassle for a short flight for me.
Good Luck =)