No, not 75 cents to a dollar, the liter bottle of soda makes 4-5 drinks, so that comes out to about 25 cents each plus tequila. I'm sure in Texas you probably get limes cheaper. I usually pay a dollar for 2-3 limes but you only need a quarter of one for each drink. I do buy bottled all natural lime juice with no sugar added it called Nellie & Joe's Key West Lime Juice, but you could use fresh. So even with the higher prices I have to pay, it's still under 40 cents and much tastier than any mix.
Now I'm itching for one, but it's such a rainy day here, I'll wait until the sun comes out.