It seems that if you are in the US then you don’t really have much in the way of choice if you want to use a fertility lubricant. Pre-seed is the foremost one and in fact the only one available on Amazon (be careful not to click on the ones for animals are there are some on there!).
Pre-seed is obviously good and a market leader but it is not cheap. When you are trying to get pregnant it seems that everything is rather expensive and the costs can add up quickly.
One way of not having to spend money on fertility lubricants is to increase your own fertile cervical mucus. There are a few ways of doing this, for example taking Evening Primrose Oil in the first half of your cycle, Drinking lots of water in the period leading up to ovulation, drinking grapefruit juice in the same time period or using a supplement like fertile CM (again adding more cost).
Although soft cups can be used without any extra lubricant, many people want to combine using them with also using a lubricant, to maximise their chances. So it seems a bit of a shame that there is not much in the way of competition in the fertility lubricant market. Perhaps someone will come up with something else soon.