It's good to have the dust shield, and it does help reduce salt spray on the rotors (which cause them to get rustier). But there's not as much splashing on the insides of the front wheels as say the rear rotors.
Here's the deal: to remove the front wheel bearing/hub, they become seized on SOOOO tight (esp here in the upper midwest), that you pretty much have to destroy them to get them off. A) It's a lot of hard pounding to remove them, B) You need to replace with a brand new one almost always. It's a lot of work and the expense of a quality hub (avoid the cheapies). C) Sometimes bearings/hubs come off easy, but usually not. The mechanic has to figure a higher number & probably didn't want to scare you with a big number just to install the dust shield (and bearing). Yer typical car owner who doesn't understand the work, is likely to think they're being ripped-off.
If your truck has it's original wheel bearings, I might be tempted to wait a yr or 2 and see if the wheel bearings get noisy and whatever other front end work it might need at that time (ball joints, CV Axles, Struts, etc ....replace those AND the bearings/hub assemblies (& both dust shields) at the same time. Ram front bearings/hubs don't last forever. If you drive it every day, there's less chance the rotors will get as rusty to the point of being a problem, as if you only drove it intermittently. All the caliper hardware is exposed anyway, even WITH a dust shield in place.
Yeah, doing a bunch of suspension work at one time will cost a king's ransom, but then it'll be done and you'll have a better driving/handling/safter pickup that'll be ready for many more trouble-free miles. And that dust shield will be in place too
