Should I price based on what I paid for equipment, or what it's actually worth today?

What it's actually worth today, not what you originally paid — buyers value equipment based on its current condition, remaining useful life, and what it would cost to replace or what it could be sold for separately, not on your original purchase price. Equipment depreciates, and in many industries what you paid years ago has little bearing on its value in a sale today.

The nuance is that this cuts both ways. Equipment can be worth less than you paid because it's aged or been heavily used, but it can also occasionally be worth more than its depreciated book value if it's still in strong working condition, if similar equipment is now more expensive to buy new, or if it's integral to producing the business's earnings rather than just sitting on a balance sheet. A buyer's own assessment, often through an independent appraisal for significant equipment, is what actually determines its treatment in the deal, not either your original cost or your book value.

Because equipment valuation directly affects how an asset sale purchase price gets allocated between different types of assets, which has its own tax consequences, it's worth having your accountant and a business lawyer involved in how equipment is valued and allocated in the agreement, rather than defaulting to either your purchase price or a rough guess.