And if others believe that Goff is as good as you seem to believe, it's going to take even more than that to move up from the mid to late teens. Remember, when the Redskins made their move, they were just moving up from #6 to #2. To date, the Rams would be trying to move up from #18.
Let's look at that trade with Washington (and I'm one that thinks Washington gave up too much). It wasn't that much of a premium over the numbers on the trade value table.
St. Louis gave the #2 pick to Washington. #2 is worth 2,600 points.
Washington sent #6 (1,600 points), #39 (510 points), and their #1s for the next two years. Therefore, Washington received a total of 2,600 points; St. Louis received 2110 points plus two future picks. It is the future picks which are harder to value.
Since you don't know what the team's draft position will be in future years, there is some guesswork involved. For the sake of this analysis, lets assume a middle of the round pick, #16. From what I have read, a pick one year in the future is valued at one-half its value in the current year, the pick two years in the future is valued even lower. For the sack of argument, let's put its value at one-fourth (half of a half). The #16 pick is worth 1,000 points so one year in the future, it would be worth 500. St. Louis would now be at a total of 2610 plus the extra two years in the future pick, which I value at 250 points, giving St. Louis 2860 total to Washington's 2600, the difference being the equivalent of the #66 pick in the current year's draft. A premium, but not a huge premium. I've always thought that the only "gouge" of Washington in that trade was the #1 pick two years in the future. The rest of the trade was even.
What gives St. Louis the ability to make a move is that extra second this year. That pick is essentially the same value as the #16 pick next year. Right now, our #1 and the two #2s are worth a total of about 1810 points, or the number #4 pick this year. Throw in our first rounder next year and we get that total up to 2310, or a bit more than the #3 pick is worth. If St. Louis wants to make the deal, they have the capital to do so, although the cost to get the #1 pick might not be worth it.
Look at San Francisco (who many think would be our main competition to move up for Goff). San Francisco's #1 and #2 are worth a total of 1960, which puts them barely ahead of us (equivalent to a late 3rd round pick) before spending future picks. We can beat them in a trade deal if we want to do so.