To replace a tie-rod end correctly, an alignment is required to adjust the toe so I can understand that but your fuel filter isn't required to be replaced until 100K miles (see manual) unless you requested one before that time. There is no "oil pan" gasket on any white engine (unless that's an error?), it's a sealant but if it was the source of your leak, the subframe must be lowered to R&R the oil pan. It wouldn't have been done w/o your approval, at least not in any shop I'm familiar with.
The cabin air filter does cost about $35 from any Volvo dealer. Volvo parts aren't in-expensive but I also wouldn't use aftermarket parts for most maintenance items, excluding a few select add-on or HP options.

One thing to consider about many indys that I've seen, from the inside too: they usually won't have anyone working there who's likely to have any real education or experience with your FWD Volvo (anyone can hang tune-up parts, brakes, etc on any car) but they'll tell you what you want to hear, mostly that they can do the same work as your dealer but for less $$$. They'll also use aftermarket parts to keep your costs down BUT those import aftermarket parts are usually of poor quality and if you have problems afterwords, you might be back at the dealer to pay (once again) to have the right OEM parts installed. A good example of this is in regards to brakes. We often see where someone has new aftermarket brake pads installed but "ever since" they're very noisy yet these people don't go back to the shop who installed those parts, they return to the dealer. The only permanent cure then that the dealer can do is to replace those pads with OEM so those customers end up paying twice for one brake job. Just a little "food for thought". Most OEM Volvo maintenance type parts last a long time with few, if any problems but I can't say that for most of the aftermarket parts I've seen on import cars, some of which are pure junk IMHO.
As for what to do if and when you go back to a dealer, they can't legally do work on your car w/o your permission so they should first inform you of what they're suggesting before you OK (approve) the work. If you then have doubts, you can either come into the shop where they can show you what they're telling you in person or you can take the car elsewhere for a second opinion.