I've been using Retin-A on and off for about 15 years. I'm 41 and used Retin-A for acne when I was younger, but now use it for improved skin appearance. Insurance pays for part of the cost of the Retin-A, so I was estimating $150/year without a discount.
I personally think Retin-A is the only topical product that really improves the texture and appearance of your skin outside of IPL or other laser treatments. I've tried other, more expensive topical products but noticed that the costs add up so fast that you might as well save up for IPL or laser treatment. I've also asked the dermatologists and laser nurses I know about Obagi, etc., and they've told me not to waste my money on anything but Retin-A or laser treatments.
I use 0.05% cream but I can't use it full strength- I have to mix it with moisturizer. Nevertheless, it seems to work great for reducing redness, scarring, age spots, dull skin, etc., by increasing cellular turnover.