It is but the telcos don't operate in a free market. Additionally, the GSM standard puts SMS messages in a low-bandwidth channel, increasing scarcity. Of course, there are technical solutions to this problem but fixing the problem is tantamount to slaughtering a cash cow and it's not done.
you can have 160 chars of 7 bit instead which costs you $0.0000625 / char instead of $0.00007143