As with any other sport, it depends on your level of engagement. If you are a rider than puts 5-miles at a shot on your bike every other week or so, you can get by with a $20.00 bike and some hand-me-down riding shorts. If, on the other hand, you are a seriously competitive bike Ninja who is competing at the State level, the cost would make most folks cringe! If you are like most semi-serious riders who put in 3K-6K annual miles, a new bike will set you back $2.5K-$7K. With some planning and a bit of compromising, you can find great deals on Craigslist...if you have the time and patience. In this case, you can find a decent ride for between $500-$2K, then add another 10-25% in new hardware to replace that which is at or past needing to be replaced.
Since we're talking price, lets talk about the cost of a bike. The
#1 argument I get from new or entry level riders is, "why would I want to spend $2,500 on a bike when I can buy a huffy for $100"? There is nothing wrong with a Huffy IF: (1) you love working on your ride before and after every ride, (2) Don't mind carrying 4-pounds of tools on every ride and (3) either ride alone all the time or don't care if you can't keep up with the rest of the group! My life is busy enough as it is without having to perform maintenance on my bike after every ride. I want to take it to the shop once a year for a thorough cleaning and tuneup. Then, when I go riding, taking the bare minimum in tools like a Park folding tool-kit that fits into a small pouch on the rear of my seat with an extra tube, patches and a couple C02 cartridges and inflater. The entire kit weighs about 1/2 pound and doesn't wiggle even when I sprint. I don't want missed shifts when I'm tired and approaching the Wall...I don't want my brakes squealing every time I slow down from a fast descent and I really don't want my chain breaking because it got caught between two gears while I'm putting 400-Watts to the pedals during a sprint! I'll work right up till the time I have to leave, jump in the truck with my bike in the back and have nothing to do but bring tire pressures up to spec before sprinting to catch up with the group as they leave the parking lot. When I ride, I know my gear will perform as it should and I rarely ever need to do anything to it because it is designed to be used and used hard for hundreds of hours between checkups! I paid my dues early on when I spent many hours tuning my bike before major rides. Today, I simply want to ride without worrying if my equipment will last till the end of a century and for that privilege, I gladly pay a premium in added cost of my steed.
I guess what I'm trying to say is, the cost of riding is directly proportional to your tolerance level for breaking down mid-ride. If you ride a $150 Huffy and ride 5-miles every other week with 1-hour in the saddle, your hourly expenses for riding will be about the same as my $3,750 bike that I ride 200-miles per week and spend 10-hours per week in the saddle! As your level of riding/competition goes up, your level for breakdowns has to go down and for that to happen you need one of two things: Either you pay someone to do the work or you pay a premium for quality components. Just know that for every rider that "evolves" from beginner to advanced, there is someone who thinks that buying a great steed is a shortcut to success, who will eventually sell that same steed at a steep discount once they figure out it just ain't so! To push an advanced level riding machine through it's paces requires literally decades of experience and conditioning! Buying the same bike that a Pro used to win a major tour won't make you a Pro! It will only drain your bank account and make some bike sales-person happy!
The best advice I can give you is to find a group you feel comfortable with and then find those riders who are much better than you and ask for help in finding a decent bike. Chances are, someone in the group has a bike they would be willing to part with that is just right for you! Once you get your feet wet and gain some experience, you will know when it is time to upgrade, assuming you didn't just hit a typical performance plateau and simply need to ride through it to the next level... but again, your advance riders in your group will help you decide if it is time for a new steed.