For the sake of this answer, I will be limiting myself to four sources: the main EP book, Transhuman, Zone Stalkers, and Sunward. This may mean that I have some missing information. The general rationale behind this is that this is the survey of all the places that talk about Earth (core, Sunward, and Transhuman), and x-risk style campaign hooks (EP book, Transhuman, and Zone Stalker). I also looked over Firewall, but couldn't find anything about Earth relics in it.
So how valuable is an Earth artifact? Some of it has to do with rarity; but the EP core rulebook has something to say about this:
A single dried flower, coin, or piece of stone from Earth can be exchanged for almost any morph or other good that is moderately difficult to create.
Now, that's not an explicit valuation, but almost any morph probably means that you're looking at a credit value of 40k credits (that's actually something like 80% of the morphs according to my reference .ods with all the Morph Recognition Guide morphs). Now, that probably depends on buyer and availability; there's nothing saying that you're getting a new morph with that, and you could very well be getting last year's Hyperbright, if that's your thing.
The other thing is that there is a potential that this price is somewhat inflated. It does seem like there is a dubious amount of value associated with this; a coin or flower petal for 40,000 credits means that smuggling back even just a crate of Earth samples is worth millions of credits; it is supposed to be incredibly dangerous in the fluff, but the fiction makes it clear that trips to and from Earth happen often enough that there's not a zero-percent success chance. According to Sunward, one-way trips down are fairly common, especially for the Reclaimers, who send down unmanned craft occasionally. Of course, this could be the result of someone simply holding off on the trigger finger, and things leaving Earth are pretty closely scrutinized (i.e. vaporized). This means that rarity is potentially an issue. Of course, authentic Earth artifacts pre-Fall might be worth mroe than authentic Earth artifacts post-Fall, now that they're all TITANy. You can factor that into your negotiations, especially if the players give up the fact that these were recently reclaimed artifacts.
In addition, looking at Transhuman it appears that Old-Earth Relics are an interest group, so clearly there are a fair number of them. One thing that that also leads me into is the thought that a lot of people who are interested in relics might be integrated pretty heavily into the New Economy. In this case, relics are valuable only for reputation boosts and traded favors; you might be able to get a morph from someone, but there's no credit value associated with it. In addition, being known as someone who works with relics (as would most likely leak eventually) and TITAN weapons could result in blacklists or garnering the wrong sort of attention. Likewise, each item will have different values in different places; those crucifixes will sell for much more in the Jovian Republic–if you can wipe any TITAN traces off of them. Coins are valuable no matter how you shake it, and amusement park tickets will be similarly valuable with a minor boost among people interested in such things. The TITAN weapon is something that could earn the attention and ire of a half-dozen authorities (including Firewall and Ozma), and even a Scum or anarchist habitat will likely be less than pleased about its presence.
Looking at Zone Stalkers, any TITAN artifact is worth in the high Expensive bracket, if not more. The exception to this would be drugs, especially Halcyons, which self-replicate (making them common), but mostly because there's one dose and they're gone, which sort of ruins the resale value. Morphgrow is actually probably the cheapest TITAN product per volume, selling at a minimum of three credits per liter for a tank of the stuff. However, this is for stuff found on Mars, not Earth. Earth-specific things, if meaningfully distinct from their Martian equivalents, could be exponentially more valuable.