Clothing for shoulder months between Winter and Summer, or mixed conditions - not cold water, but maybe cool water and medium to warm air temperature, etc. - you have to figure out what your in-between conditions are and what provides adequate protection. In between water temperatures are still dangerous for extended immersion (particularly in terms of attitude, as they can tilt many paddlers toward less care in terms of immersion survivability). Shoulder seasons can also be extra dangerous because weather can be volatile and water temperatures can be subject to rapid and not always anticipated decreases.
When you see prices that seem low compared to other products there usually is a reason, most likely you are looking at less expensive neoprene with overlock or flatlock stitching which will not keep your nearly as protected from leakage and faster flush through. And the neoprene may very possibly be more water absorbant and less flexible than higher quality, more expensive options. 
Before you rely too heavily on these styles for warmth you should test them in the conditions you intend to use them in. Farmer Johns/Janes can be deceptive - providing a fair amount of warmth while you are dry, but providing surprisingly little protection when wet or submerged particularly if they are the style with long zippers - often such zippers and/or the suits simply allow too much rapid water entry and exit to slow heat loss. If paired with a snug top, water flow-thru rate can be reduced.
Many other wetsuit brands offer farmer johns, janes, and shorties