They'd probably do it for free. It was seen as protecting American business interests. It was argued that it would protect art by incentivizing storage and restoration of old works. There are counter arguments to these arguments, but it wasn't a super controversial bill.
The biggest part of lobbying is just getting people to notice your issue. Meeting the right people and getting the right language crafted is like 9/10ths of the process. Not all (probably not even most) lobbying is bribery.
I'd be hesitant to make the latter statement in isolation. Given my experiences with various levels of "important individuals" over the years, the money is MOST useful for opening that door in the first place.
It's a lot easier to offer a group of high power individuals a 5 star dinner with a realistic expectation they'll who up, as opposed to cold calling them as just another average joe. Once that connection is established, the relationship is much less active bribery and much more "let's have a little chat and see if we can't find something mutually agreeable"; although to be frank, I'm not sure I'd say the latter is any less worrying.
The biggest part of lobbying is just getting people to notice your issue. Meeting the right people and getting the right language crafted is like 9/10ths of the process. Not all (probably not even most) lobbying is bribery.