If chlorine is what worries you, then you don't need an RO system.
Your city water has chlorine in it, and you need to remove that chlorine >before< it would get to any RO membrane anyway (because it will destroy the membrane rather quickly). The typical setup would be:
city water -> sediment filter (to reduce silt that would jam up the following filter) --> granulated activated carbon (GAC) filter (to get rid of the chlorine and organic chemicals (e.g pesticides, etc) --> drinking water tap (and ice maker). You could put an RO membrane after the carbon filter, it will remove some things that the other filters won't (esp dissolved inorganic minerals, like salt, etc--could be important if you have a water softener). You could even install a UV light downstream of that to kill viruses and bacteria--but the city's chlorine will have done that already, the only other source would be a colony in your carbon filter--that's a good reason to change them annually.
If you go with a simple sediment and granulated carbon filter, your drinking water will taste about like it tastes if you use a Britta filter--which most people find to be very good. If you are on a typical city water system, this is all you need. The cost of the sediment filter (replace every 6 mos) and a good granulated carbon filter (replace annually) will be less than $75 total per year, which is quite a bit cheaper, more convenient, and better for your health and the environment than bottled water.
I'm on a well with hard water, and I built quite a complicated system: water softener, sediment filters, carbon filter, RO, polishing filter, UV light. The drinking water tastes great. If you are on city water you don't need to go to all that trouble--the city has done most of the work for you. If you haven't already done so, get a report from your city and see what is actually in the water--they have to tell you.
Lastly--the brand of sytem you buy will have a big impact on the cost of supplies (remember--what you asked about!). Some newer systems have convenient (and propietary) filters in which the filter body and the internal media are all disposable. Remove the old one with a quarter-turn, insert the new one with a quarter turn and you are done. It takes just a minute or two. My system uses filter bodies that are permanent: I unscrew them with a big plastic wrench, dump out the old filter cartridge, clean them out (soap and a bit of bleach), clean out the top of the housing into which they screw, insert new filter media into the body, put some lube on the O-ring, and screw them into place. The filters for these are standard, generic, and widely available, they cost about 1/2 what the fancy (and more convenient) proprietary filters cost. It takes me about 30 minutes, start to finish, to change two filters, so that's an hourly rate of about $75/hour (after taxes). As a bonus, I'm much more certain that these filters will still be available as long as I need them.