I will add..the straw bales are not only cheap , but...easy on your arrows,easy pull, long lasting,eco friendly;)
Just look for the tightest bale you can find or "IF" you are in good with the farmer...ask if they can adjust the tension for a tighter bale. If not...you can rachet strap square and round bales if needed.
Most likely have that knowledge , but some may not. Like many of you I have run the gamut on this topic....Used mats , foam blocks , stuffed bags, hay bales, THICK cardboard ....for me nothing is as user friendly as straw bales.
Only thing better imho is the old (expensive)Saunders Indian Cord Matt .(picture from on-line) Really wish someone would start making these again in the states at a reasonable price. Back in the day..every archery range had them & or straw, and for good reason. They are easy on arrows, quiet , holdup to the outdoor exposure , and LAST ....
Best with your quest my friend .......