If you want to keep shooting slide film you need to be on the lookout for deals. I comb eBay for short dated and recently dated films -- recently picked up 15 rolls of Velvia and Provia 120 for $5.50 / a roll. B&H last year sold off a ton of short dated 35mm stock, also for $5 a roll. The trick is to be prepared to buy when it's a good deal, even if you don't think you need more film (and this is why I had to take up re-selling camera gear...)
Processing at Citizen's Photo in Portland, where I mail all my color film to is $6.50. I always save up film until I have about a dozen rolls and shipping costs about $5 each way. So, I mostly save it for special occasions. But all in, about $12 a roll won't kill me. And there's nothing like medium format slides. If shooting slide film cost me $30 a roll, I wouldn't do it either. But there are things you can do to keep costs down.