There are much more of these so-called "trash for benefit" cards, and if you want to compare them, i suggest you just take a look at the
Dominion Wiki.
Personally i play Dominion for quite some time, and i too find
Forge (as well as Expand) to be absurdly expensive. They might not work for 6$ (i don't know about that), but unless Quarry or a lucky Coppersmith happens, they never seem to make a difference for me.
Trading Post on the other hand is a trasher, but it also gives you money (+2$) and gains a card. It is pretty good at increasing your "money density". Strangely i thought about it just today and found it interesting that the card is better the worse your deck is - more noticeably than other trashers, i daresay.
Develop often forces you to gain cheap cards you don't want, especially if you trash more expensive cards (trashing a Gold for example is usually just giving you a worse card on top of your deck). It can help you build an "engine" under certain circumstances, i guess, but i must admit that i never got it to work really well, personally.
Remodel on the contrary is happy to trash expensive cards, and you would usually refrain from trashing Coppers with it (often you would have to gain an Estate), but trashing a Gold at the endgame can be a clever move. It is - in a way - more flexible than Develop.