Looking for affordable truck/coupler assemblies

At one time the big Lionel parts suppliers had a good supply of plastic arch bar type for $5-7 a pair. I bought all I could but that supply is now gone. If there is such a animal today I'd like to know myself. Good luck. 

Yes rolling stock trucks can be expensive.  At many train shows you can find beat up and broken cars often in boxes full of them.  I just pick out a beat up freight car, examine it, if they are in good shape the car is used for the trucks and the body is scrapped.  The usual cost for these type of junk cars is $2-$5 and I often get the later metal trucks with the needle bearing axles.  A quick spray of Krylon black satin restores the original look. The next day I lube them and they are as good as new.  As for passenger car replacement trucks they are very difficult to find and when you do find them the sellers ask more than I am willing to pay. Toy parts are only worth a few bucks.

"Does any one know where I can get truck/coupler assemblies without dropping 20 to $25 a pair? " 

Yes. eBay.

I have bought  bunch, over the years. Still do. Shop around; prices vary. Modern, MPC, Post War - all can be useful, especially when I convert cars from 2- to 3-rail.

(I have trouble resisting some of those beautiful, so-called "2-rail" (wheel sets can be changed - I've done it) passenger and tender trucks, especially when they are unpainted brass. Beautiful. But that's my weakness.)

Also, Lionel PW coupler upgrade units - often NOS, and easy to add to most any truck with the same wheelbase, can be very useful. Prices vary, of course. (Post War: best 3RO couplers ever made.)

Don't forget "grab bag lots" of parts, which often include wheel sets, Lionel PW coupler upgrade units, trucks. Bargains show up regularly. 

Weaver is gone, and we're looking for an oasis in the Sahara.