If you just want to make buying a lot of cards worthwhile you could simply cut the extra Buys and merely do a Event that does cost reduction:
$2
+1 Buy
This turn cards cost 1 less, but no less than 0.
If you buy 2 cards it does nothing, if you buy 3 it yields +2, if you buy 4 it yields +6 and so on.
I am still skeptical, there are probably many overpowered combinations if you implement cost reduction as an Event. There is Ferry so DXV probably thought about or tried general cost reduction in Event form for Adventures yet didn't do it for good reasons.
I'll change it so that the base is $3 instead, that way you're breaking even if you buy it thrice (but can be doing better if you have other sources of +buy).
At a base price of $3 the Event behaves like this:
# times you buy the Event - cumulated cost - benefit in Coins -
net Coin yield - net Coin yield of Travelling Fair
1 | 3 | 2 |
-1 | -2
2 | 7 | 6 |
-1 | -4
3 | 12 | 12 |
0 | -6
4 | 18 | 20 |
+2 | -8
same stuff with one extra Buy before you buy the Event:
1 | 3 | 3 |
0 | -2
2 | 7 | 8 |
+1 | -4
3 | 12 | 15 |
+3 | -6
4 | 18 | 24 |
+6 | -8
I am still not a fan of free Buys and would advocate to use the $4 base price version as it makes Buys sometimes costly and thus makes the Event more similar to Travelling Fair. But at least this version is less crazy than the $2 monster.