Not for a permanently spaceworthy ship
I looked it up in my old Spelljammer box set for AD&D 2nd Edition, and the new rules greatly simplify the creation of
Spelljamming helms and vessels. And you’re right - it’s gotten a lot cheaper to get into space.
Creating a Spelljammer helm with a spell is technically more expensive in 5E; in AD&D, Create minor helm was a fifth or sixth level spell (for priests or wizards, respectively) with no costly material component - it just required a suitable chair, and even that was optional for the priest version of the spell. However, the catch is that the old version of the spell did not create a permanent helm; the minor helm from the spell only lasts one week per level of the caster (or one hour per level, in the case of the priest spell cast without a suitable chair). From the Concordance of Arcane Space booklet, page 21 and 24 (the spell is given for each class):
This spell does not replace the need for a permanent helm onboard, and is used primarily as a back-up system or in emergency situations.
Methods for creating permanent helms (or their alternatives, which did exist in AD&D) are not detailed, but they can be salvaged, found as rare treasure, or - most reliably - you can buy one from the Arcane. This is a spacefaring culture of merchants, who were renamed in later editions; they appear in third and now fifth edition as the Mercane (thanks to KRyan and Danila Smirmnov in the comments for info on this). A minor helm costs 100,000gp, while a major helm costs 250,000gp. The difference is in how efficiently they convert the magical energy of the user into motive power; minor helms give a ship’s rating (which measures speed and power) of 1/3 the caster’s level, major ones 1/2. The cheapest hull listed in the book to fit one in is a Coaster, which costs 5,000gp, for a minimum cost of 105,000gp plus crew.
For a cheaper option you could buy a gnomish helm - they cost 50,000gp, but 40% of them don’t work at all, and the rest need constant repairs to keep them going. Or, if you can find one, you could buy a much slower nonmagical engine of limited power for 10,000gp. That brings down the price to 15,000gp, but it’s a pretty substandard ship that might not be able to get into space, depending on the size of your planet.
For comparison, horse barding was actually cheaper in AD&D 2E: for a plate set it cost 2,000gp, or a bit over 1/8 of the cheapest spacegoing ship. (Thanks to John Dallman for providing this figure in the comments.)
You probably don’t want a spelljamming vessel that small
Of note, in both old and new editions of Spelljammer, having a small ship is dangerous. Most obviously, a small ship is easier to destroy, having fewer hit points and a lower (or nonexistent) damage threshold. In the old edition small ships had various limitations, not least on weaponry and crew; the Coaster was also hard to steer and imposed a penalty on ship rating as a result. If two ships touch the gravity plane of the larger one overrides the smaller one. (The new edition changes this to the one with the most hit points, which except in extreme cases will usually have the same result.)
Perhaps most dangerously, a small ship has a very small air envelope. This doesn’t matter too much if you stick to the crew size limit, but if someone falls overboard you have a very small window to bring them back onboard before they’re left behind.
So there are plenty of reasons a small seagoing ship might not be a good choice for spelljamming, and most ships are space galleons for a reason.