Discussions tend to focus on either low or high tech tanks, but there's actually a very broad spectrum between the two.
My tanks range from no to mid-tech but are easily moved up and down the spectrum by hanging which light bar goes on which tank, adjusting the fert schedule to match and--occasionally--re-arranging the plant layout. A high light loving plant that was surviving but not spectacular under low light levels might be moved into a prominant position once it's given enough light to make it worth showcasing, or plants prefering lower light moved into more shaded areas if the light levels are greatly increased.
How far you want to move up the spectrum depends entirely on where you want to end up as it may or may not require injected C02 and high ferts. Fast growth, lush carpets, deep reds usually require C02 but...if you haven't yet, check out the low-tech forum. Lots of great tanks showing what's possible with low to moderate light levels that would only require you to upgrade your lights and invest in moderate fertilization.
Costs are equally variable. Sleek, streamlined, automated brand name lights run high--but you can get the same results much cheaper with DIY options. Similarly, dry ferts are cheap in the use, but require a bit more in initial layout to buy all the ingredients in bulk. Your best bet is to figure out what you want to achieve and then start scaling your costs from there. In general, though, you want to buy lights that reach the top end of what you want; it's far easier and cheaper to moderate the affect of a too strong light system than the reverse.